Systems and methods for transeptal cardiac procedures, including separable guidewires

ABSTRACT

Systems and methods for transeptal cardiac procedures are disclosed. A patient treatment device in accordance with a particular embodiment includes an elongated first intravenous guidewire that includes a first branch and a second branch fixably secured relative to the first branch at a first location. The device can further include an elongated second intravenous guidewire that is movable relative to at least one of the first and second branches between a first position in which the first and second branches are releasably secured relative to each other by the second guidewire at a second location, and a second position in which the first and second branches are separated from each other at the second location.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. Provisional ApplicationNo. 60/977,837, filed Oct. 5, 2007 and incorporated herein by reference.

TECHNICAL FIELD

The present disclosure is directed generally to systems and methods fortranseptal cardiac procedures, including separable guidewires.

BACKGROUND

The human heart is a complex organ that requires reliable, fluid-tightseals to prevent de-oxygenated blood and other constituents receivedfrom the body's tissues from mixing with re-oxygenated blood deliveredto the body's tissues. FIG. 1A illustrates a human heart 100 having aright atrium 101, which receives the de-oxygenated blood from thesuperior vena cava 116 and the inferior vena cava 104. The de-oxygenatedblood passes to the right ventricle 103, which pumps the de-oxygenatedblood to the lungs via the pulmonary artery 114. Re-oxygenated bloodreturns from the lungs to the left atrium 102 and is pumped into theleft ventricle 105. From the left ventricle 105, the re-oxygenated bloodis pumped throughout the body via the aorta 115.

The right atrium 101 and the left atrium 102 are separated by aninteratrial septum 106. As shown in FIG. 1B, the interatrial septum 106includes a primum 107 and a secundum 108. Prior to birth, the primum 107and the secundum 108 are separated to form an opening (the foramen ovale109) that allows blood to flow from the right atrium 101 to the leftatrium 102 while the fetus receives oxygenated blood from the mother.After birth, the primum 107 normally seals against the secundum 108 andforms an oval-shaped depression, i.e., a fossa ovalis 110.

In some infants, the primum 107 never completely seals with the secundum108, as shown in cross-sectional view in FIG. 1C and in a left side viewin FIG. 1D. In these instances, a patency often having the shape of atunnel 112 forms between the primum 107 and the secundum 108. Thispatency is typically referred to as a patent foramen ovale or PFO 113.In most circumstances, the PFO 113 will remain functionally closed andblood will not tend to flow through the PFO 113, due to the normallyhigher pressures in the left atrium 102 that secure the primum 107against the secundum 108. Nevertheless, during physical exertion orother instances when pressures are greater in the right atrium 101 thanin the left atrium 102, blood can inappropriately pass directly from theright atrium 101 to the left atrium 102 and can carry with it clots, gasbubbles, or other vaso-active substances. Such constituents in theatrial system can pose serious health risks including hemodynamicproblems, cryptogenic strokes, venous-to-atrial gas embolisms,migraines, and in some cases even death.

Traditionally, open chest surgery was required to suture or ligate a PFO113. However, these procedures carry high attendant risks, such aspostoperative infection, long patient recovery, and significant patientdiscomfort and trauma. Accordingly, less invasive techniques have beendeveloped. Most such techniques include using transcatheter implantationof various mechanical devices to close the PFO 113. Such devices includethe Cardia® PFO Closure Device, Amplatzer® PFO Occluder, and CardioSEAL®Septal Occlusion Device. One potential drawback with these devices isthat they may not be well suited for the long, tunnel-like shape of thePFO 113. As a result, the implanted mechanical devices may becomedeformed or distorted and in some cases may fail, migrate, or evendislodge. Furthermore, these devices can irritate the cardiac tissue ator near the implantation site, which in turn can potentially causethromboembolic events, palpitations, and arrhythmias. Other reportedcomplications include weakening, erosion, and tearing of the cardiactissues around the implanted devices.

Another potential drawback with the implanted mechanical devicesdescribed above is that, in order to be completely effective, the tissuearound the devices must endothelize once the devices are implanted. Theendothelization process can be gradual and can accordingly take severalmonths or more to occur. Accordingly, the foregoing techniques do notimmediately solve the problems caused by the PFO 113.

Still another drawback associated with the foregoing techniques is thatthey can be technically complicated and cumbersome. Accordingly, thetechniques may require multiple attempts before the mechanical device isappropriately positioned and implanted. As a result, implanting thesedevices may require long procedure times during which the patient mustbe kept under conscious sedation, which can pose further risks to thepatient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D illustrate a human heart having a patent foramen ovale (PFO)in accordance with the prior art.

FIG. 2 illustrates a catheter positioned proximate to a PFO fortreatment in accordance with several embodiments of the disclosure.

FIGS. 3A-3J illustrate a process for closing a PFO in accordance with anembodiment of the disclosure.

FIG. 4 is a partially schematic, isometric illustration of a process forclosing a PFO via a trans-primum procedure in accordance with anembodiment of the disclosure.

FIGS. 5A-5D are schematic, isometric illustrations of a process forclosing a PFO using a trans-primum procedure in accordance with anotherembodiment of the disclosure.

FIGS. 6A-6M illustrate guidewires configured to center in a PFO tunnelin accordance with embodiments of the disclosure.

FIG. 7A is a flow diagram illustrating a process for pre-loading apenetrating guidewire in accordance with an embodiment of thedisclosure.

FIG. 7B-7G illustrate devices suitable for applying a pre-load to apenetrating guidewire in accordance with several embodiments of thedisclosure.

FIGS. 8A-8L illustrate electrode devices that include conductivefilaments in accordance with several embodiments of the disclosure.

FIGS. 9A and 9B illustrate an electrode device that includes aconductive sheet configured in accordance with an embodiment of thedisclosure.

FIGS. 10A and 10B illustrate an electrode device including a conductivematerial that deploys in an “umbrella” fashion.

FIGS. 11A-11C illustrate an electrode device and an inflatable memberfor deploying the electrode device.

FIGS. 12 and 13 illustrate electrode devices that are deployed withinflatable members in accordance with further embodiments of thedisclosure.

FIG. 14 illustrates an electrode device that is deployed in anumbrella-like fashion in accordance with another embodiment of thedisclosure.

FIGS. 15A-15B illustrate an electrode device that includes a tubularportion and fingers configured in accordance with an embodiment of thedisclosure.

FIGS. 16A-16B illustrate an electrode device having nested tubularportions with inner and outer fingers in accordance with anotherembodiment of the disclosure.

FIGS. 17A-17B illustrate an electrode device having a spiral woundtubular portion and associated flange in accordance with an embodimentof the disclosure.

FIGS. 18A-18B illustrate an electrode device having a woven tubularportion and associated flange in accordance with an embodiment of thedisclosure.

FIGS. 19A and 19B illustrate an electrode device having knitted fibersforming a tubular portion and a flange in accordance with anotherembodiment of the disclosure.

FIGS. 20A and 20B illustrate an electrode device having fibers woven toform a tubular portion and a flange in accordance with yet anotherembodiment of the disclosure.

FIG. 21 is a partially schematic, cross-sectional illustration of acatheter arranged to apply a compressive force on an electrode device inaccordance with a particular embodiment of the disclosure.

FIG. 22 is a partially schematic illustration of a threaded device forapplying a compressive force on an electrode device in accordance withan embodiment of the disclosure.

FIG. 23 is a partially schematic, cross-sectional illustration of anarrangement that includes a slider for applying a compressive force onan electrode device in accordance with yet another embodiment of thedisclosure.

DETAILED DESCRIPTION

A. Introduction

Aspects of the present disclosure are directed generally to methods anddevices for drawing portions of cardiovascular tissue together, sealingthe portions to each other, and controlling the performance of thesetasks. Much of the discussion below is provided in the context ofsealing patent foremen ovales (PFOs). However, in other embodiments,these techniques may be used to treat other types of cardiac tissueand/or tissue defects. The energy to seal the PFO is generally providedby an energy transmitter. For purposes of discussion, much of thefollowing description is provided in the context of energy transmittersthat include electrodes configured to seal cardiac tissue by deliveringradio frequency (RF) energy. In other embodiments, the energytransmitters can have other arrangements and can deliver other types ofenergy, for example, microwave energy, laser energy or ultrasoundenergy.

In general, many of the techniques and associated devices describedbelow include advancing a catheter into the right atrium of thepatient's heart, piercing the septum between the right atrium and theleft atrium, and placing an electrode or other energy transmitter in theleft atrium. The energy transmitter applies energy to the septum to sealthe PFO, optionally with the assistance of a balloon or other inflatablemember, and is then drawn back through the septum. The catheter can thenbe withdrawn from the patient's body, leaving no foreign objects behind.A residual hole in the septum remaining after the electrode is withdrawnfrom the left atrium to the right atrium is expected to close over ashort period of time as a result of the body's natural healing response.

Many techniques and devices described in detail in one or more of thefollowing sections may be combined with techniques and/or devicesdescribed in the same section and/or other sections. Several detailsdescribing devices or processes that are well-known to those of ordinaryskill in the relevant art and often associated with such devices andprocesses are not set forth in the following description for purposes ofbrevity. Those of ordinary skill in the relevant art will understandthat further embodiments may include features not disclosed in thefollowing sections, and/or may eliminate some of the features describedbelow with reference to FIGS. 2-23.

FIG. 2 is a schematic, not-to-scale illustration of the generalcomponents of a system 220 used to treat a patient in accordance withseveral embodiments of the disclosure. The system 220 generally includesone or more patient treatment devices, a term which, as used herein,includes devices that provide direct therapeutic benefits, and/orassociated functions, including but not limited to, diagnosticfunctions, feedback functions, and/or positioning functions. The system220 can include one or more guidewires 250 that are directed into thepatient via an introducer 226, and are then threaded through thepatient's vascular system to the heart 100. In the illustratedembodiment, the guidewire 250 enters the right atrium 101 from theinferior vena cava 104, and in other embodiments, the guidewire 250 canenter the right atrium 101 or other heart chamber from other vessels.One or more guidewires may also pass into the left atrium 102. One ormore catheters 230 are then threaded along the guidewire 250 viacorresponding lumens to treat a PFO 113 (e.g., the PFO tunnel 112)located between the primum 107 and the secundum 108 of the patient'sseptum 106. The catheter lumen(s) can be flushed with saline or anotherappropriate biocompatible fluid, either continuously or at selectedintervals, to prevent clot formation and/or to lubricate the relativemotion between the catheter(s) and devices within the lumens.

The catheter 230 typically includes a distal end 232 within thepatient's body, a working portion 233 toward the distal end 232, and aproximal end 231 that extends outside the patient's body. A controller221 controls the functions carried out by the catheter 230 and the restof the system 220, and can include an energy delivery controller 223 tocontrol RF or other energy transmitted to the patient, an inflatablemember controller 222 to control the operation of one or more inflatablemembers in the patient, a sensor feedback unit 225 to receive diagnosticinformation, and other controllers 224 to control other functions, forexample, the motion of various guidewires and/or other elements of thesystem 220, and/or fluid delivery to elements of the system 220. Arepresentative handheld controller configured for such purposes isdescribed in co-pending U.S. application Ser. No. 12/246,349, filedconcurrently herewith and incorporated herein by reference. When theenergy transmitter or delivery device includes an electrode, it may beoperated in a monopolar manner, in which case a return electrode 280 ais located remotely from the PFO 113. For example, the return electrode280 a can include a patient pad located at the back of the patient'sleft shoulder. In other embodiments, the electrode can operate in abipolar manner, in which case the return electrode is generally locatedat or close to the PFO 113.

For purposes of organization and ease of understanding, the followingdiscussion is arranged in five sections in addition to the presentSection A. Section B describes overall techniques and tissue sealingdevices for sealing a patient's PFO. Section C describes self-centeringguidewires used to position the tissue sealing devices, and Section Ddescribes systems and techniques for penetrating the septal tissue.Section E describes electrodes configured to seal the PFO, and Section Fdescribes systems and techniques for clamping the septal tissue as it issealed. Similar disclosures are included in the following U.S.Applications, filed concurrently herewith and incorporated herein byreference: U.S. application Ser. No. 12/246,366; U.S. application Ser.No. 12/246,361; and U.S. application Ser. No. 12/246,358.

B. General Techniques and Systems for Treating a PFO

FIGS. 3A-3I are enlarged cross-sectional views of the heart regionsaround a PFO, and illustrate representative techniques and associateddevices for sealing the PFO in accordance with a particular embodiment.Beginning with FIG. 3A, a practitioner passes a right atrial guidewire250 a into the right atrium 101 of the patient's heart 100 in accordancewith a particular embodiment. Optionally, the practitioner can continueto advance the right atrial guidewire 250 a into the superior vena cava.The practitioner then passes a left atrial guidewire 250 b into theright atrium 101, through the PFO tunnel 112 and into the left atrium102. Accordingly, the left atrial guidewire 250 b is positioned in thetunnel 112 between the primum 107 and the secundum 108. Suitable imagingprocesses (e.g., transthoracic ultrasound or TTE, intra-cardiac echo orICE, transesophageal echo or TEE, fluoroscopy, and/or others) known tothose of ordinary skill in the relevant art may be used to position theguidewires 250 a, 250 b and/or other devices used during the procedure.

In another embodiment, the left atrial guidewire 250 b is routed asdescribed above, but before the right atrial guidewire 250 a isintroduced. The right atrial guidewire 250 a is instead pre-loaded intoa delivery catheter (described later with reference to FIG. 3C), and thedelivery catheter, with the right atrial guidewire 250 a on board, isthreaded along the left atrial guidewire 250 b to the right atrium 101(e.g., at or near the junction between the right atrium 101 and theinferior vena cava). Once the delivery catheter is in the right atrium101, the right atrial guidewire 250 a can be deployed to the locationshown in FIG. 3A.

In FIG. 3B, the practitioner has threaded a self-centering guidewire 250c along the left atrial guidewire 250 b and into the tunnel 112.Alternatively, the self-centering guidewire 250 c can be pre-loaded intothe delivery catheter (described later with reference to FIG. 3C) andboth can be advanced together along the left atrial guidewire 250 b.This latter arrangement, e.g., in combination with pre-loading the rightatrial guidewire 250 a as described above, can prevent the left atrialguidewire 250 b and the right atrial guidewire 250 a from becomingtwisted. In either embodiment, the self-centering guidewire 250 c caninclude a first branch 251 and a second branch 252 positioned around anenclosed region 249. In a particular aspect of this embodiment, thefirst branch 251 is hollow so as to receive the left atrial guidewire250 b along which the self-centering guidewire 250 c is passed. Thefirst and second branches 251, 252 can be at least somewhat compliantand resilient and can accordingly spread or tighten the primum 107laterally, as indicated by arrow S, upon being introduced into thetunnel 112. By stretching the primum 107, the self-centering guidewire250 c can draw the primum 107 toward the secundum 108. In addition, thebranches 251, 252 can be symmetric relative to a central axis C and canaccordingly center the self-centering guidewire 250 c within the PFOtunnel 112. Furthermore, the closed shape provided by the first andsecond branches 251, 252 can provide the guidewire 250 c with a degreeof lateral rigidity along the axis identified by arrow S. Accordingly,when the guidewire 250 c is placed in the tunnel 112, the resilienceprovided by the primum 107 and/or the secundum 108 can force theguidewire 250 c to assume the orientation shown in FIG. 3B, e.g., withthe generally flat plane of the enclosed region 249 “sandwiched” betweenand facing toward the primum 107 on one side and the secundum 108 on theother. The lateral rigidity of the self-centering guidewire 250 c whenit is deployed can also prevent it from twisting, which in turn can makeit easier for the practitioner to accurately seal the tunnel 112.

Turning next to FIG. 3C, the practitioner has threaded a deliverycatheter 230 a along the right atrial guidewire 250 a and theself-centering guidewire 250 c, which is in turn threaded along the leftatrial guidewire 250 b, as discussed above. Or, as discussed above, theright atrial guidewire 250 a and the self-centering guidewire 250 c canbe pre-loaded into the delivery catheter 230 a and deployed once thedelivery catheter 230 a has been threaded along the left atrialguidewire 250 b until it is positioned in the right atrium 101. Ineither embodiment, the delivery catheter 230 a can include a rightatrial guidewire opening 234 a that receives the right atrial guidewire250 a, and a left atrial guidewire opening 234 b that receives theself-centering guidewire 250 c and the left atrial guidewire 250 b overwhich the self-centering guidewire 250 c is passed. In this embodiment,the self-centering guidewire 250 c has a generally ellipticalcross-sectional shape, and accordingly, the left atrial guidewireopening 234 b has a similar shape. With this arrangement, theself-centering guidewire 250 c is “keyed” to the delivery catheter 230a. Accordingly, the delivery catheter 230 a has a known orientationrelative to the self-centering guidewire 250 c when the deliverycatheter 230 a reaches the position shown in FIG. 3C. The upwardprogress of the delivery catheter 230 a can be limited by a “tree crotcheffect” provided by the delivery catheter 230 a positioned on one sideof the septal limbus 117, and the combined left atrial guidewire 250 band self-centering guidewire 250 c on the other side of the limbus 117.In addition, radiopaque markers M can be located at the left atrialguidewire opening 234 b and the point at which the branches 251, 252bifurcate. In a particular embodiment, the markers M can therefore beco-located or nearly co-located when the delivery catheter 230 a hasbeen properly advanced. Once the delivery catheter 230 a has theposition shown in FIG. 3C, the right atrial guidewire 250 a canoptionally be withdrawn, or it can remain in place for additional steps,including for the remainder of the procedure.

As noted above with reference to FIG. 2, the overall system can includea return electrode positioned close to the PFO. FIG. 3C illustrates areturn electrode 280 b carried by the delivery catheter 230 a so as tooperate in a bipolar manner with an electrode delivered in accordancewith an embodiment of the disclosure. In a particular aspect of thisembodiment, the return electrode 280 b can include an electricallyconductive coating or sleeve positioned at the outside of the deliverycatheter 230 a, and coupled to an electrical return terminal (e.g., atthe controller 221 shown in FIG. 2) via a lead wire (not visible in FIG.3C). In another embodiment, the return electrode 280 b can have otherarrangements and/or configurations in which it is positioned close tothe primum 107 and/or the secondum 108.

In FIG. 3D, a positioning catheter 230 b (which is housed within andmovable relative to the delivery catheter 230 a) is deployed from thedelivery catheter 230 a. In this embodiment, the positioning catheter230 b is deployed by applying an axial force to it, causing it to buckleor bend outwardly through a corresponding slot (not visible in FIG. 3D)in the outer surface of the delivery catheter 230 a. Accordingly, thepositioning catheter 230 b can assume the shape shown in FIG. 3D. In onearrangement, the distal end of the positioning catheter 230 b iseccentrically connected to a pivot axle 235, which allows thepositioning catheter 230 b to rotate as indicated by arrow R as itbuckles. As the positioning catheter 230 b rotates, it can position theexit opening of a lumen 239 to face outwardly from the delivery catheter230 a.

The lumen 239 can also face directly toward the secundum 108, and can bealigned with the central axis C above the limbus 117, as a result of thefeatures of the self-centering guidewire 250 c, the delivery catheter230 a and the positioning catheter 230 b. In particular, theself-centering guidewire 250 c can be centered within the tunnel 112,with the plane defined by the enclosed region 249 facing directly towardthe secundum 108. Because the self-centering guidewire 250 c has agenerally flat shape (and can optionally stretch the primum 107), theprimum 107 and the secundum 108 can tend to keep the self-centeringguidewire 250 c from rotating or twisting about its lengthwise axisrelative to the tunnel 112. In addition, the branches 251, 252 of theself-centering guidewire 250 can be secured to each other in a mannerthat resists twisting. Because the self-centering guidewire 250 c iskeyed with the delivery catheter 230 a, as discussed above withreference to FIG. 3C, the delivery catheter 230 a is prevented or atleast restricted from rotating about its lengthwise axis relative to thetunnel 112. Accordingly, when the positioning catheter 230 b isdeployed, the lumen 239 can face directly toward the secundum 108, e.g.,at an orientation of from about 80° to about 135°, and in a particularembodiment, about 105°. It is expected that in at least someembodiments, an orientation of about 105° results in a subsequent tissuepenetration operation that effectively penetrates the secundum 108 andthe primum 107 with a reduced likelihood for penetrating other tissue inthe left atrium. In addition, this orientation can increase thelikelihood of penetrating the primum 107, e.g., when the tunnel 112 isrelatively short. The lumen 239 can also be located at the lateralcenter or approximate center of the tunnel 112 (e.g., measured laterallyalong a lateral axis L that is generally transverse to the central axisC). The “tree-crotch effect” described above can act to locate the lumen239 above the limbus 117, but not so high that the lumen 239 is abovethe primum 107.

In a particular embodiment, a limbus stop 236 is connected to thepositioning catheter 230 b. As the positioning catheter 230 b rotates,the limbus stop 236 rotates outwardly to the position shown in FIG. 3D.When the practitioner applies an axial (e.g., upward) force to thedelivery catheter 230 a, the limbus stop 236 can nudge up against thelimbus 117. In other embodiments, the limbus stop 236 can be eliminated.In still further embodiments, the delivery catheter 230 b can include alimbus marker 236 a, in addition to or in lieu of the limbus stop 236.The limbus marker 236 a can be a pin or other element made from gold,platinum or another radiopaque material. The limbus marker 236 a canhelp guide the operator to correctly position the delivery catheter 230a relative to the limbus 117 before penetrating the secundum 108. Thelimbus 117 itself may be illuminated with a contrast agent. In manycases, the delivery catheter 230 a and other components illustrated inFIG. 3D may be formed from plastics or other materials that do notreadily appear during fluoroscopy processes. Accordingly, the limbusmarker 236 a can provide a readily visible locator on the deliverycatheter 230 a to aid the practitioner during a tissue sealingprocedure. The limbus marker 236 a can be positioned at a known locationalong the length of the delivery catheter 230 a, for example 4 mm belowthe axis along which a penetrating guidewire is deployed. Furtherdetails of the penetrating guidewire are described below with referenceto FIG. 3E.

As shown in FIG. 3E, a penetrating guidewire 250 d or other penetratingdevice or member can be deployed from the positioning catheter 230 b.The penetrating guidewire 250 d can include a penetrating tip 253 thatpenetrates through the secundum 108 and the primum 107, so as to crossthe entire septum 106 into the left atrium 102. In a particularembodiment, the penetrating tip 253 can include an RF electrode that isadvanced through the septum 106 in a stepwise fashion described infurther detail below with reference to FIGS. 7A-7F. The electrode canhave a generally spherical or ball-type shape, with a diameter of up toabout 1.0 mm. In other embodiments, the penetrating tip 253 can haveother shapes or configurations, and/or can be advanced using othertechniques, and/or can employ other non-RF methods for penetrating theseptum 106. Such configurations include, but are not limited to apenetrating tip 253 having a sharp distal end that pierces the septum106. For example, the penetrating tip can include one or more razor-likeelements or blades that score the septum 106. The blades can deploylaterally outwardly, and/or can be deployed from an inflatable balloon.In other embodiments, the tip 253 can include rotoblades, laser energyemitters, and/or ultrasound energy emitters.

In FIG. 3F, the practitioner advances an electrode catheter 230 c alongthe penetrating guidewire 250 d from the right atrium 101 into the leftatrium 102. The electrode catheter 230 c can include a dilator 237 thattemporarily stretches the hole initially created by the penetratingguidewire 250 d to allow additional components to pass into the leftatrium 102. These components can include an inflatable member 270 (showncollapsed) and an electrode device 280. In a particular embodiment, thepenetrating guidewire 250 d can form a hole having a diameter of aboutone millimeter, and the dilator 237 can have a diameter of about twomillimeters to temporarily stretch the hole to a diameter of about twomillimeters. When the electrode catheter 230 c and the penetratingguidewire 250 d are later withdrawn, the hole can relax back to adiameter of about one millimeter. In other embodiments, these dimensionscan have other values. In any of these embodiments, the dilator 237and/or the penetrating tip 253 can include radiopaque markings forenhanced visibility during fluoroscopic visualization.

In FIG. 3G, the practitioner has inflated the inflatable member 270(e.g., with saline or another suitable inflation medium) in the leftatrium 102, and has also deployed the electrode device 280. In aparticular embodiment, the electrode device 280 includes a conductivecoating applied to a proximally facing surface of the inflatable member270. The inflatable member 270 can be formed from a non-stretch materialso that it maintains a predefined shape (e.g., the cylindrical shapeshown in FIG. 3G) when inflated. This arrangement can also prevent orrestrict the conductive coating from delaminating, flaking, and/orotherwise detaching from the inflatable member 270. Other suitableelectrode shapes and configurations are described later with referenceto FIGS. 8A-20B and in at least some of these embodiments, theinflatable member 270 is eliminated.

Prior to engaging the electrode device 280 with the septum 106, thepractitioner can withdraw the self-centering guidewire 250 c and theleft atrial guidewire 250 b by separating or opening the first andsecond branches 251, 252 at a separation location 255, allowing them topass downwardly around opposite sides of the electrode catheter 230 cand into the left atrial guidewire opening 234 b. Further details ofembodiments for performing this task are described later with referenceto FIGS. 6A-6K.

In FIG. 3H, the self-centering guidewire 250 c (FIG. 3G) and the leftatrial guidewire 250 b (FIG. 3G) have been removed, and the practitionerhas applied an axial force to the electrode catheter 230 c in agenerally proximal direction P. The axial force draws the inflatablemember 270 and the electrode device 280 snugly up against the primum107. This force can also clamp the primum 107 against the secundum 108,and can clamp both the primum 107 and the secundum 108 between theelectrode device 280 and a backstop surface 238. In an embodiment shownin FIG. 3H, the backstop surface 238 includes the outwardly facing,conductive external surface of the delivery catheter 230 a, e.g., thereturn electrode 280 b. Accordingly, the electrode device 280 canoperate in a bipolar manner via the return electrode 280 b. In otherembodiments, the backstop surface 238 can have other locations and/orarrangements. For example, the backstop surface 238 can be separate fromthe delivery catheter 230 a, and/or can be electrically non-conductive,so that the electrode device 280 operates in a monopolar manner.

With the electrode device 280 in the position shown in FIG. 3H, thepractitioner can apply electrical energy (e.g., a varying electricalcurrent) to the electrode device 280. In representative embodiments,electrical energy is applied to an electrode device 280 having adiameter in the range of about 3 mm to about 30 mm, at a frequency inthe range of about 100 KHz to about 5 MHz for a period of up to 10minutes (e.g., in a particular embodiment, from about 30-120 seconds).The energy can be provided at a rate in the range of from about 10 Wattsto about 500 Watts, and in a particular embodiment, in the range of fromabout 40 Watts to about 50 Watts. The foregoing ranges are suitable forthe electrode device 280 shown in FIG. 3H, and other electrodes as well,including the electrode device 580 f described later with reference toFIG. 8J. Different sizes and shapes of the PFO (or other tissue defect)will typically determine the particular electrode device size and/orenergy delivery parameters. For example, the electrode device 280 canhave a diameter of from about 7 mm to about 20 mm, and in a particularembodiment, about 9 mm. In a particular embodiment, the electricalenergy can be applied to a 9 mm diameter electrode device at a frequencyof about 450 KHz, for about 5 seconds, at a rate of from about 300 Wattsto about 400 Watts. The electrical energy can be applied with asinusoidal waveform, square waveform, or another periodic waveformshape, generally with a crest factor of from about one to about fifteen.RF energy provided to the electrode device 280 is received by theadjacent tissue so as to heat both the primum 107 and the secundum 108.The heat can at least partially fuse, glue, cement, or otherwise seal,join or connect the primum 107 and the secundum 108 together, forming aseal 118 that partially or completely closes the PFO tunnel 112 betweenthe left atrium 102 and the right atrium 101.

After the tissue fusing and/or sealing process has been completed, theinflatable member 270 can be collapsed and the electrode catheter 230 c,the positioning catheter 230 b and the penetrating guidewire 250 d canbe withdrawn into the delivery catheter 230 a, as is shown in FIG. 3I. Aresidual opening 119 may remain in the seal 118 as a result ofwithdrawing the electrode catheter 230 c and penetrating guidewire 250 d(FIG. 3H) back through the septum 106 from the left atrium 102 to theright atrium 101. The residual opening 119 is typically very small(e.g., on the order of one millimeter) and is expected to close quicklyas a result of the body's normal healing process. The practitioner thenwithdraws the delivery catheter 230 a from the patient's body. In othercases in which the seal 118 may initially be incomplete for otherreasons, it is also expected that the seal will be sufficient to allowthe body's normal healing processes to complete the closure, generallyin a short period of time.

FIG. 3J is a partially schematic, cross-sectional illustration of thedelivery catheter 230 a taken substantially along line 3J-3J of FIG. 3I.As shown in FIG. 3J, the delivery catheter 230 a can include multiplelumens, including an electrode catheter lumen 279 that carries thepositioning catheter 230 b (FIG. 3F) and the electrode catheter 230 c(FIG. 3F) housed within it. The delivery catheter 230 a can also includea right atrial guidewire lumen 278 that houses the right atrialguidewire 250 a (FIG. 3C), and a self-centering guidewire lumen 275 thathouses the self-centering guidewire 250 c (FIG. 3C). A return electrodelumen 277 houses a return electrode lead 276 that is in turn coupled tothe return electrode 280 b (FIG. 3C). Contrast agent can be delivered tothe PFO region via any of the foregoing lumens (e.g., the returnelectrode lumen 277), and/or via an interstitial region 274 betweenneighboring lumens.

In other embodiments, techniques similar at least in part to thosedescribed above with reference FIGS. 3A-3I may be used to form tissueseals in different manners. For example, referring now to FIG. 4, thedelivery catheter 230 a can be located so that the positioning catheter230 b is below the limbus 117 and facing the primum 107, rather thanabove the limbus 117 and facing the secundum 108, as described abovewith reference to FIGS. 3A-3I. Accordingly, when the penetratingguidewire 250 d and the electrode catheter 230 c are deployed, they passthrough the primum 107 but not the secundum 108. The resulting tissueseal 418 will typically be smaller than the seal 118 described abovewith reference to FIG. 3I because a greater portion of the electrodedevice 280 is located below the limbus 117 and does not face directlytoward the secundum 108. However, this arrangement may be suitable whereit is expected that the smaller seal 418 will still have the desiredeffect on the PFO tunnel 112 (e.g., tunnel sealing), and/or where it isundesirable to penetrate the secundum 108.

FIGS. 5A-5D illustrate another arrangement for sealing the PFO tunnel112 without penetrating the secundum 108. As shown in FIG. 5A, the rightatrial guidewire 250 a is positioned in the right atrium 101, and theleft atrial guidewire 250 b and the self-centering guidewire 250 c arepositioned in the tunnel 112 and the left atrium 102. In FIG. 5B, adelivery catheter 530 a is threaded along the right atrial guidewire 250a and the self-centering guidewire 250 c. A right atrial guidewireopening 534 a and a left atrial guidewire opening 534 b are positionedso that as the delivery catheter 530 a is passed along the guidewires250 a-250 c, it enters the PFO tunnel 112. A penetrating guidewire 550d, when deployed, accordingly penetrates only the primum 107 and not thesecundum 108.

After the penetrating guidewire 550 d has passed through the primum 107,the delivery catheter 530 a is removed, as shown in FIG. 5C. The rightatrial guidewire 550 a is then also removed. In FIG. 5D, thepractitioner threads a positioning catheter 530 b along the penetratingguidewire 550 d, and deploys an electrode catheter 530 c from thepositioning catheter 530 b to pass through the primum 107. The electrodecatheter 530 c can include an electrode device 280 and an inflatablemember 270 generally similar to those described above with reference toFIG. 3G. When drawn up against the primum 107, the electrode device 280can clamp the primum 107 and the secundum 108 against a backstop surface538 of the positioning catheter 530 b. The resulting seal 518 has ashape and location generally similar to the seal 418 described abovewith reference to FIG. 4.

C. Self-Centering Guidewires and Associated Systems and Methods

In many of the embodiments described above, a self-centering intravenousguidewire can be used to locate the sides, edges and/or lateralboundaries of the PFO tunnel 112, thus allowing the practitioner to moreprecisely locate the tissue seal at the center of the tunnel 112, e.g.,along an axis transverse or generally transverse to the flow axis of thetunnel 112. FIGS. 6A-6K illustrate representative embodiments ofguidewires, generally referred to as self-centering guidewires, suitablefor performing this function. Beginning with FIG. 6A, a self-centeringguidewire 650 a (generally similar to the self-centering guidewire 250 cdescribed above) includes a first branch 651 a and a second branch 652 athat are fixedly secured relative to each other at a first location 654a. When the self-centering guidewire 250 c is positioned in a catheter,the first and second branches 651 a, 652 a are squeezed toward eachother. The first and second branches 651 a, 652 a can be formed from aflexible, resilient material, e.g., Nitinol or another material thattends to assume the shape shown in FIG. 6A when the self-centeringguidewire 650 a is deployed. When in the deployed position, the firstand second branches 651 a, 652 a can be located in the same generallyflat plane. The first branch 651 a can have a hollow or tubularconstruction, which allows it to be threaded along the left atrialguidewire 250 b. The practitioner advances the self-centering guidewire650 a along the left atrial guidewire 250 b by applying an axial forceto a distal portion of the self-centering guidewire 650 a while the leftatrial guidewire 250 b is held in place. The delivery catheter 230 a(FIG. 3C) is then passed along the self-centering guidewire 650 a.

The self-centering guidewire 650 a can also include a connector tube 656at a second location 655 a. The connector tube 656 can be fixedlyattached to the second branch 652 a, but not to the first branch 651 a.The left atrial guidewire 250 b can pass through both the tubular firstbranch 651 a and the connector tube 656, so that the first branch 651 aand the second branch 652 a form a generally closed shape around anenclosed region 649. The left atrial guidewire 250 b can accordinglyprevent the branches 651 a, 652 a from separating at the second location655 a. The practitioner then directs the penetrating guidewire 250 dthrough the septum (as described above with reference to FIG. 3E) andthrough the enclosed region 649 between the first and second branches651 a, 652 a. Next, the practitioner can pass the electrode catheter 230c (a portion of which is shown in FIG. 6A) over the penetratingguidewire 250 d, as was discussed above with reference to FIG. 3F, andthrough the enclosed region 649.

To remove the self-centering guidewire 650 a without disturbing theelectrode catheter 230 c, the practitioner can withdraw the left atrialguidewire 250 b from the connector tube 656 by moving the left atrialguidewire 250 b in a proximal direction P. Without the left atrialguidewire 250 b securing the first branch 651 a to the connector tube656, the first branch 651 a can at least disengage from the connectortube 656, and in a particular embodiment, can spring away from thesecond branch 652 a as indicated by arrow E, and as shown in dashedlines in FIG. 6A. Accordingly, the first branch 651 a and the secondbranch 652 a can form an open shape having a gap 657. With thisconfiguration, the self-centering guidewire 650 a can be withdrawn in aproximal direction P so that the first branch 651 a passes along oneside of the electrode catheter 230 c and the second branch 652 a,separated from the first branch by the gap 657, passes along theopposite side of the electrode catheter 230 c. The practitioner can thenwithdraw the self-centering guidewire 650 a and the left atrialguidewire 250 b into the delivery catheter 230 a (FIG. 3H) while theelectrode catheter 230 a remains in position. In another embodiment, thefirst branch 651 a can disengage from the connector tube 656 withoutinitially moving to form the gap 657. In this case, the first branch 651a can contact the electrode catheter 230 c as the self-centeringguidewire 650 is drawn proximally, causing the first branch 651 a todeflect away from and around the electrode catheter 230 c.

In a particular embodiment, the first and second branches 651 a, 652 acan enclose a generally hexagonally-shaped enclosed region 649 havingrounded or arcuate corners. Accordingly, the first and second branches651 a, 652 a can move smoothly into and out of the PFO tunnel 112 (FIG.3H). The rounded or arcuate portions of the first branch 651 a can alsoaccommodate the left atrial guidewire 250 b positioned within it withoutcausing the left atrial guidewire 250 b to kink or bind. Each of thefirst and second branches 651 a, 651 b can have generally parallel sideportions 646 toward the center of the self-centering guidewire 650 a,and converging end portions 645 toward the first and second locations654 a, 655 a. This arrangement can be particularly suitable when theopposing edges of the PFO tunnel 112 are generally parallel. In otherembodiments, other shapes (e.g., elliptical shapes and/or other arcuateshapes) can also be suitable for such tunnel topologies. In stillfurther embodiments, the enclosed region 649 can have other shapes,e.g., shapes with non-parallel side portions 646, depending on theparticular patient's tunnel characteristics. In any of theseembodiments, the first and second locations 654 a, 654 b (and/or otherlocations of the self-centering guidewire 650 a) can include radiopaquemarkings for enhanced visibility during fluoroscopic visualization.

FIG. 6B illustrates a self-centering guidewire 650 b having a centralenclosed region 649 formed by a first branch 651 b and a second branch652 b, with the left atrial guidewire 250 b passing through, rather thanaround, the enclosed region 649, in accordance with another embodiment.In a particular aspect of this embodiment, the first and second branches651 b, 652 b are fixedly secured relative to each other at a firstlocation 654 b, and are releasably secured relative to each other by theleft atrial guidewire 250 b at a second location 655 b. At the secondlocation 655 b, the first branch 651 b includes a first connector tube656 a, and the second branch 652 b includes a second connector tube 656b having two portions 648 a, 648 b separated by a space 647 (e.g., inthe form of a slot or other receptacle 640). The first connector tube656 a is removably received in the space 647, e.g., in a tab-and-slotarrangement. In particular, the first connector tube 656 a can include atab 641 having surfaces generally parallel to the plane of the enclosedregion 649, and the second connector tube 656 b can have receptacle orslot surfaces that are also generally parallel to the plane of theenclosed region 649. Accordingly, the first and second branches 651 b,652 b can interlock at the second location 655 b when the tab 641 isreceived in (e.g., snugly engaged with) the receptacle 640. Thetab-and-slot arrangement can restrict or eliminate relative twistingbetween the two branches 651 b, 652 b, thus maintaining the generallyflat, planar shape of the enclosed region 649. The left atrial guidewire250 b passes through both the first and second connector tubes 656 a,656 b when the self-centering guidewire 650 b forms the enclosed region649. To remove the self-centering guidewire 650 b without disturbing theelectrode catheter 230 c, the practitioner can withdraw the left atrialguidewire 250 b proximally (as indicated by arrow P) from the firstconnector tube 656 a, allowing the first branch 651 b to release and, inat least one embodiment, spring outwardly, as indicated by arrow E. Thefirst and second branches 651 b, 652 b can then be passed around theelectrode catheter 230 a and out of the patient's body withoutdisturbing the electrode catheter 230 c.

FIG. 6C illustrates a self-centering guidewire 650 c configured inaccordance with another embodiment in which the electrode catheter 230 cis used to separate a first branch 651 c from a second branch 652 c at asecond location 655 c. The self-centering guidewire 650 c can include atube 656 c that is threaded along the left atrial guidewire 250 b as theself-centering guidewire 650 c is advanced into the heart. Prior toseparating the first and second branches 651 c, 652 c, the first branch651 c extends around most of the enclosed region 649 and is received inan opening at the end of the second branch 652 c, at the second location655 c. When the self-centering guidewire 650 c is moved in a proximaldirection P toward the electrode catheter 230 c, a contact portion 658of the first branch 651 c contacts the electrode catheter 230 c. As thepractitioner applies an additional axial force to the self-centeringguidewire 650 c, the electrode catheter 230 c forces the end of thefirst branch 651 c out of the opening at the end of the second branch652 c, as indicated by arrow O, causing the first branch 651 c todisengage, and in at least one embodiment, spring outwardly as indicatedby arrow E. With the self-centering guidewire 650 c in thisconfiguration, it can be removed from around the electrode catheter 230c. In other embodiments, mechanisms other than the opening at the end ofthe second branch 652 c can be used to releasably connect the first andsecond branches 651 c, 652 c at the second location 655 c. For example,magnets carried by each of the first and second branches, 651 c, 652 ccan be used to perform this function.

FIG. 6D illustrates a self-centering guidewire 650 d that is similar insome respects to the self-centering guidewire 650 c described above withreference to FIG. 6C. In particular, an embodiment of the self-centeringguidewire 650 d includes a first branch 651 d attached to a secondbranch 652 d at a first location 654 d. The first branch 651 d includesan end that is removably received in a tubular portion of the secondbranch 652 d at a second location 655 d. A central tube 656 d isthreaded along the left atrial guidewire 250 c and extends generallyacross the enclosed region 649, but is not attached to the first andsecond branches 651 d, 652 d, except at the first location 654 d. Theincreased axial length of the tube 656 d can further guide and align theself-centering guidewire 650 d relative to the left atrial guidewire 250c. When the self-centering guidewire 650 d is to be removed, thepractitioner can move it in a proximal direction P until a contactportion 658 contacts the electrode catheter 230 c. When the practitionermoves the self-centering guidewire 650 d by an additional amount in theproximal direction P, the first branch 651 d pulls out of the secondbranch 652 d, separating and/or springing open as indicated by arrow Eand opening a gap 657 through which the electrode catheter 230 c passesas the self-centering guidewire 650 d is removed.

FIG. 6E is a partially broken illustration of a self-centering guidewire650 e configured in accordance with still another embodiment. In oneaspect of this embodiment, the guidewire 650 e includes a first branch651 e and a second branch 652 e that each have a fixed position relativeto the other at a first location 654 e and are removably securedrelative to each other at a second location 655 e. At the first location654 e, the first and second branches 654 e, 655 e can be connected to aferrule 659 that slideably receives a connector tube 656 e which is inturn threaded along the left atrial guidewire 250 c. The connector tube656 e can include a connector 673 toward its distal end. The connector673 can include a first aperture 674 a that receives the first branch651 e, and a second aperture 674 b that receives the second branch 652e. Flat surfaces 675 on the ends of the branches 651 e, 652 e snuglymate with corresponding surfaces within the connector 673 to resist thetendency for the branches 651 e, 652 e to twist out of the plane shownin FIG. 6E. When the self-centering guidewire 650 e is deployed into thepatient's PFO, the connector tube 656 e and the attached connector 673have a position that is proximal (as indicated by arrow P) from theposition shown in FIG. 6E, so that the end of the first branch 651 e isreceived in the first aperture 674 a, and the end of the second branch652 e is received in the second aperture 674 b. Accordingly, the firstand second branches 651 e, 652 e are temporarily secured in positionrelative to each other at the second location 655 e. When theself-centering guidewire 650 e is to be removed, the practitioner canslide the connector tube 656 e and the connector 673 in a distaldirection relative to the ferrule 659 and along the left atrialguidewire 650 c (as indicated by arrow D) to disengage the connector 673from the first and second branches 651 e, 652 e. The self-centeringguidewire 650 e can then be removed from the patient in a mannergenerally similar to that described above.

FIGS. 6F-6J illustrate an overall arrangement for a self-centeringguidewire and a controller in accordance with a particular embodiment ofthe disclosure. Aspects of the embodiment can facilitate deploying theself-centering guidewire (and the right atrial guidewire) from thedelivery catheter once the delivery catheter is located in the patient'sheart to reduce or eliminate the likelihood for these guidewires tointerfere with each other (e.g., twist together). This arrangement isalso expected to be less likely to disturb the position of theself-centering guidewire once it is in the PFO because the (stiffer)delivery catheter is advanced along the self-centering guidewire foronly a short distance, e.g., the distance between (a) the entrance ofthe vena cava to the heart, and (b) the PFO tunnel.

Beginning with FIG. 6F, the self-centering guidewire 650 f can include afirst branch 651 f and a second branch 652 f fixedly secured relative toeach other at a first location 654 f. For example, both branches 651 f,652 f can be fixedly connected to a shaft 685. The first and secondbranches 651 f, 652 f can be releasably secured relative to each otherat a second location 655 f by a connector 673. A deployment tube 686 isattached to the connector 673 and slides within the shaft 685 to changethe configuration of the self-centering guidewire 650 f from a stowedposition (shown in FIG. 6F) in which the guidewire 650 f is configuredto be carried in a delivery catheter, to a deployed position describedin further detail below with reference to FIG. 6G.

The operation of the self-centering guidewire 650 f can be controlled bya guidewire controller 680 that includes a housing 681, a deploymentknob 682, and a connector knob 683. The deployment knob 682 ismanipulated to change the self-centering guidewire 650 f from the stowedposition shown in FIG. 6F to the deployed position. The connector knob683 is manipulated to release the first and second branches 651 f, 652 fat the second location 655 f. The shaft 685 and the guidewire controller680 are threaded over the left atrial guidewire 250 b, and a lubricantfitting 684 can provide saline or another suitable, biocompatiblelubricant to facilitate relative motion between the various componentsof the guidewire 650 f and the guidewire controller 680. The guidewireis typically threaded through a catheter (e.g., the delivery catheter230 a shown in FIG. 3C), but for purposes of clarity, the catheter isnot shown in FIGS. 6F-6K.

The housing 681 can include an L-shaped deployment slot 687 whichreceives a deployment pin 688 carried by the deployment knob 682. Todeploy (e.g., expand) the self-centering guidewire 650 f, the operatorrotates the deployment knob 682 as indicated by arrow R1 so that thedeployment pin 688 moves circumferentially within the deployment slot687. An internal spring then forces the deployment knob 682 away fromthe housing 681 so that the deployment pin 688 moves axially within thedeployment slot 687. The deployment knob 682 is connected to thedeployment tube 686, which is in turn connected to the connector 673.Accordingly, when the deployment knob 682 moves axially as indicated byarrow T1, the connector 673 moves axially as indicated by arrow T2.

FIG. 6G illustrates the self-centering guidewire 650 f in its deployedposition, after the deployment knob 682 has been manipulated in themanner described above with reference to FIG. 6F. The first and secondbranches 651 f, 652 f can be formed from a shape-memory material (e.g.,Nitinol) so as to bend toward the shape shown in FIG. 6G in the absenceof an external force. In this configuration, the first and secondbranches 651 f, 652 f can spread and/or tighten the tissue of the primumin a manner generally similar to that described above, and an electrodecan be moved through the atrial septum into the left atrium so as toseal or at least partially seal the PFO tunnel, also in a mannergenerally similar to that described above.

One aspect of an embodiment shown in FIGS. 6F-6G is that the deploymentknob 683 is spring loaded and is not locked once it is released. As aresult, the self-centering guidewire 650 f will automatically adjust toPFO tunnels having different widths. For example, if the tunnel isrelatively narrow, the branches 651 f, 652 f may not spread apart to thefullest possible extent, and the deployment knob 683 may not travelaxially to the fullest possible extent. In this manner, theself-centering guidewire can automatically adjust to any tunnel having awidth greater than or equal to the spread of the branches 651 f, 652 fin the undeployed position (FIG. 6F), and less than or equal to thespread of the branches 651 f, 652 f in the fully deployed position (FIG.6G).

After the electrode has been positioned for tissue sealing (e.g., asdiscussed above with reference to FIG. 3H), the first and secondbranches 651 f, 652 f can be released at the second location 655 f toallow the self-centering guidewire 650 f to be withdrawn from thepatient's body. To release the first and second branches 651 f, 652 f,the operator rotates the connector knob 683 as indicated by arrow R2,causing a connector pin 690 (which depends from the connector knob 683)to rotate circumferentially within a corresponding C-shaped connectorslot 689 carried by the deployment knob 682. This motion can unlock theconnector knob 683 and allow it to move axially. The practitioner thenmoves the connector knob 683 axially relative to the deployment knob 682and the housing 681, as indicated by arrow T3, against a resistanceforce provided by an internal spring. The locking function provided bythe connector slot 689 and the resistance provided by the internalspring can prevent the connector knob 683 from being operatedinadvertently. As the connector knob 683 is advanced axially, theconnector 673 moves axially away from the branches 651 f, 652 f, asindicated by arrow T4. Once the connector knob 683 has been advancedaxially as indicated by arrow T3, it is rotated as indicated by arrow R3so as to move the connector pin 690 circumferentially clockwise withinthe connector slot 689. Once the practitioner has rotated the connectorknob 683 as indicated by arrow R3, the connector 673 is secured in anunlocked position, described below with reference to FIG. 6H.

FIG. 6H illustrates the self-centering guidewire 650 f and the guidewirecontroller 680 with the self-centering guidewire 650 f in an unlockedconfiguration. In this configuration, a connector tube 656 f, which isslideably housed within the deployment tube 686, and which is connectedto the connector knob 683, has pushed the connector 673 axially alongthe left atrial guidewire 250 b to release the first and second branches651 f, 652 f at the second location 655 f. Once in this configuration,the entire self-centering guidewire 650 f can be removed from thepatient's body by moving the guidewire controller 680 as a unit in anaxial distal manner as indicated by arrows T5. Because the first andsecond branches 651 f, 652 f are no longer secured at the secondlocation 655 f, they can readily pass around the electrode catheter 230c, in a manner generally similar to that described above. The branches651 f, 652 f can then collapse as they are pulled proximally through acatheter, e.g., the delivery catheter 230 a shown in FIG. 3C.

FIG. 6I is a partially schematic, cross-sectional illustration of theshaft 685, taken generally along lines 6I-61 of FIG. 6H. As discussedabove with reference to FIG. 3C, the shaft can have an elliptical orother non-round cross-sectional shape so as to maintain its orientationrelative to the catheter from which it extends (e.g., the deliverycatheter 230 a shown in FIG. 3C). The shaft 685 can be formed from aflexible material (e.g., a plastic) and can include multiple lumens thathouse corresponding components of the self-centering guidewire 650 f.For example, the shaft 685 can include a control lumen 691 a that housesthe deployment tube 686, the connector tube 656 f, and the left atrialguidewire 250 b in a generally concentric, annular fashion. Each ofthese components can move relative to the other within the control lumen691 a. The shaft 685 can further include a first branch lumen 691 b thathouses the first branch 651 f of the self-centering guidewire 650 f, anda second branch lumen 691 c that houses the second branch 652 f. Thebranches 651 f, 652 f can be secured to the inner surfaces of thecorresponding lumens 691 b, 691 c, so that they do not move relative tothe shaft 685.

FIG. 6J is a partially schematic, partially broken illustration of theself-centering guidewire 650 f illustrating details of particularcomponents. At the first location 654 f, the self-centering guidewire650 f includes a ferrule 695 that fixedly secures the first and secondbranches 651 f, 652 f to each other, e.g., via one or more spot welds.The generally rigid ferrule 695 abuts and/or is attached to thegenerally flexible shaft 685. The deployment tube 686 can slide relativeto the shaft 685 at the first location 654 f, and is connected to a pairof tabs 692 at the second location 655 f. The tabs 692 snugly engagewith corresponding flat surfaces 675 of the first and second branches651 f, 652 f. The connector tube 656 f, which is slideably positionedwithin the deployment tube 686, is attached to the connector 673, whichin turn includes a tip 693 and a sleeve 694. The tip has an opening(e.g., a through-hole) to accommodate the left atrial guidewire 250 b.The sleeve 694 fits around the distal ends of the first and secondbranches 651 f, 652 f to keep the flat surfaces 675 engaged with thetabs 692. This arrangement can significantly reduce the tendency for thebranches 651 f, 652 f to twist out of the plane of FIG. 6J. When thedeployment tube 686 is moved axially in either direction indicated byarrow T6, the connector 673, the connector tube 656 f, and the first andsecond branches 651 f, 652 f at the second location 655 f move as a unitrelative to the first location 654 f. When the connector tube 656 f ismoved axially as indicated by arrow T4, the sleeve 694 slides off thefirst and second branches 651 f, 652 f, allowing the first and secondbranches 651 f, 652 f to disengage from the tabs 692 so that theself-centering guidewire 650 f can be removed from around the electrodecatheter 230 c (FIG. 6H) and removed from the patient's body, asdescribed above with reference to FIG. 6H. In other embodiments, theself-centering guidewire 650 f can include other arrangements thatselectively lock the branches 651 f, 652 f at the second location 655 f,and resist twisting when locked, and that selectively unlock thebranches 651 f, 652 f to allow the guidewire 650 f to be withdrawn.

FIG. 6K is a partially schematic, cross-sectional illustration of theguidewire controller 680. The housing 681 of the guidewire controller680 is rigidly attached to the shaft 685, and both the guidewirecontroller 680 and the shaft 685 are threaded over the left atrialguidewire 250 b. The deployment tube 686 is attached to a first fitting697 a which is in turn forced by a deployment knob spring 696 a intoengagement with the deployment knob 682. Accordingly, the deploymentknob spring 696 a can facilitate the axial motion of the deployment knob682 as indicated by arrow T1, and as described above with reference toFIG. 6F.

The connector tube 656 f, which is slideably positioned within thedeployment tube 686, is connected to a second fitting 697 b which is inturn connected to the connector knob 683. A connector knob spring 696 bforces the connector knob 683 to the position shown in FIG. 6K, so thatthe practitioner must overcome this force to move the connector tube 656f (and the associated connector 673), as described above with referenceto FIG. 6G.

One feature of at least some of the foregoing embodiments is that theyinclude a guidewire having two resilient separable portions (e.g.,branches). An advantage of this feature is that it allows each portionto apply a relatively small, moderate, or otherwise non-tearing forceagainst opposite sides or edges of the PFO tunnel, which can bothstretch the tunnel and center the guidewire. When the practitioner thenpenetrates the septum with the penetrating guidewire and the electrodecatheter, he or she can do so with greater assurance that the electrodeor other energy delivery device is centered or approximately centeredlaterally in the tunnel. Because the branches of the self-centeringguidewire are separable, the guidewire can be removed from its centeredposition without disturbing the electrode catheter or the tissue bondformed by the electrode catheter.

Another feature of at least some of the foregoing embodiments is thatthe branches, when connected, can define a generally planar enclosedshape. This shape can tend to sandwich directly between the primum andthe secundum, as discussed above with reference to FIG. 3D, so that theguidewire tends not to rotate or twist once in position in the PFOtunnel. This is unlike existing guidewires having separate prongs, whichmay allow the guidewire to twist once it is in the PFO tunnel. Inaddition, at least some of the foregoing embodiments include connectorsthat snugly yet releasably secure the distal ends of the branchesrelative to each other. This is also unlike some existing guidewireshaving prongs with distal ends that are partially captured, but are notconstrained in a manner that adequately resists twisting. For example,the flat surfaces 675 securely mated with the corresponding surfaces ofthe connector shown in FIG. 6E are expected to significantly stiffen theguidewire 650 f against twisting about its major axis. The flat surfaces675 and corresponding tabs 692, in combination with the surroundingsleeve 694 are also expected to achieve this result. In addition, theconnector 673 can prevent the distal ends from inadvertently beingreleased as the guidewire 650 f is moved axially, proximally and/ordistally, during a positioning procedure. Accordingly, embodiments ofthe guidewire described above can allow the practitioner to moreaccurately position additional devices, e.g., penetrating guidewiresand/or energy transmitters.

Another feature of at least some of the foregoing embodiments is thatthe self-centering guidewire can automatically align with the main axisof the tunnel (e.g., the axis running the length of the tunnel, fromentry to exit), even if the cross-section of the tunnel varies. Forexample, FIG. 6L illustrates a right atrial view of the self-centeringguidewire 650 f in a PFO tunnel 112 having diverging tunnel walls. Theflexible nature of the branches 651 f, 652 f allows them to conform tothe orientation of the diverging walls, while flat portions 654 f of thebranches 651 f, 652 f maintain contact with the walls. Because the flatportions 654 f are pre-formed to be flat, they will generally remainflat when the guidewire 650 f assumes the shape shown in FIG. 6L in adiverging tunnel. FIG. 6M illustrates a right atrial view of theself-centering guidewire 650 f in a PFO tunnel having converging walls.Again, the flexible nature of the branches 651 f, 652 f can allow themto conform to the converging orientation of the walls, while the flatportions 654 f of the branches maintain contact with the tunnel walls.In particular embodiments, the branches 651 f, 652 f can includefeatures that enhance this capability. For example, the branches 651 f,652 f can include bends 653 f on either side of the flat portions 654 fthat preferentially allow the flat portions 654 f to pivot relative tothe distal and proximal portions of the branches 651 f, 652 f. The bends653 f can include pivot joints, weaker (e.g., smaller diameter) regionsof the branches 651 f, 652 f, or other suitable arrangements.

D. Devices and Methods for Penetrating Tissue

In many of the foregoing embodiments, the self-centering guidewire isused to locate the penetrating guidewire (or other penetrating member)and the electrode catheter (or other energy transmitter) relative to thePFO tunnel. In many cases, it is desirable to advance the penetratingguidewire incrementally so as to control the motion of the penetratingtip and the rate at which the tip passes through the septum. Severalembodiments are described below in the context of penetrating guidewiresthat deliver RF energy to perform tissue penetration. In otherembodiments, the penetrating guidewire can deliver other types ofenergy, e.g., ultrasound energy, microwave energy, laser energy and/orphysical force (e.g., via a sharpened tip).

FIG. 7A illustrates a process 760 for performing this technique inaccordance with a particular embodiment. Process portion 762 includesadvancing the penetrating guidewire into the right atrium. In processportion 764, one or more characteristics of the right atrial blood aresensed. For example, in a particular embodiment, process portion 764includes sensing an impedance of an electrical circuit that includes thepenetrating guidewire and the right atrial blood. The impedance valuecan then be used as a basis for comparison to the circuit impedance whenthe penetrating guidewire is (a) within the septal tissue and/or (b)through the septal tissue.

In process portion 766, the penetrating guidewire is advanced by apreselected or predetermined distance unit. In a particular embodiment,the distance unit can be one millimeter, and in other embodiments, thedistance unit can have other values. In any of these embodiments, thedistance unit can be less (and in some cases, significantly less) thanthe thickness of the tissue through which the guidewire will pass. Thedistance unit can be measured outside the patient's body, e.g., at theproximal end 231 of the catheter 230 shown in FIG. 2.

Process portion 768 includes sensing the environment adjacent to thepenetrating guidewire, and determining whether the adjacent environmentis tissue, rather than blood. This process can include determining theimpedance of the electrical circuit described above, and comparing theimpedance to a predetermined value, for example, the impedancedetermined in process portion 764. In at least some cases, thepenetrating guidewire will exit the delivery catheter directly into theseptal tissue, and so the tissue will be sensed without advancing thepenetrating guidewire any further. However, if tissue is not sensed inprocess portion 768, the penetrating guidewire is advanced an additionaldistance unit (process portion 766).

If tissue is sensed, then the penetrating guidewire is advanced by adistance unit to place a designated preload on the penetrating guidewire(process portion 770). For example, once the penetrating guidewire hasencountered tissue, advancing the penetrating guidewire by an additionaldistance unit can cause the wire to bow and/or stretch the tissueagainst which it is abutted. In a particular embodiment, the distanceunit by which the penetrating guidewire is advanced can be the same,whether the penetrating guidewire is passing through right atrial blood,or through tissue. In other embodiments, the distance units can bedifferent, depending on whether the penetrating guidewire is approachingthe tissue, up against the tissue, or within the tissue. For example,the distance unit can be greater when the penetrating guidewire isapproaching the tissue than when it is against and/or within the tissue.The preload can have a value selected based on parameters that includepatient physiology and/or characteristics of the penetrating guidewire.In particular embodiments, the preload can have a value in the range offrom about 0.01 pounds to about 0.5 pounds. In a particular embodimentin which the penetrating guidewire has a diameter of about 0.013 inchand a generally spherical tip with a diameter of about 0.030 inches, thepreload can be about 0.15 pounds.

In process portion 772, an energy pulse or a series of pulses is appliedto the penetrating guidewire to ablate the tissue against which thepenetrating guidewire abuts. The pulses can include a single pulse, aburst of pulses, and/or a series of pulse bursts. The pulses can be RFenergy pulses, or pulses of other types of energy, for example,ultrasound energy. As the penetrating guidewire advances into theablated hole made in process portion 772, the preload placed upon theguidewire in process portion 770 is released. In process portion 774,the penetrating guidewire is advanced an additional distance unit e.g.,to place a new preload on the guidewire prior to ablating additionaltissue.

Process portion 776 includes determining whether a distance limit hasbeen reached, e.g., whether the guidewire has been advanced by or to atarget value. In particular embodiments, the distance limit cancorrespond to a maximum expected thickness of the septum, or a maximumlateral dimension of the left atrium. Accordingly, process portion 786can be used to prevent the penetrating guidewire from passing throughthe left atrium and into the left wall of the heart. If the distancelimit has been reached, the process 760 stops at process portion 780. Ifnot, then process portion 768 includes determining whether left atrialblood is sensed, e.g., by sensing the impedance of the circuit describedabove. If so, this indicates that the penetrating guidewire has passedentirely through the septum. The penetrating guidewire can then beadvanced to the distance limit to provide room for additional devicesdeployed along the penetrating guidewire in the left atrium.Accordingly, the process 700 can return to process portion 774. If leftatrial blood is not sensed, then the process returns to process portion772, and additional tissue is ablated in an incremental manner untilleft atrial blood is sensed.

FIG. 7B schematically illustrates a representative apparatus suitablefor advancing the penetrating guidewire in accordance with an embodimentof a method described above with reference to FIG. 7A. The apparatus caninclude a guidewire advancer 710 a that incrementally advances thepenetrating guidewire 250 d into and through the septum 106, e.g.,through the primum, the secundum, or both. The guidewire advancer 710 acan include an actuator 711 a that is operatively coupled to thepenetrating guidewire 250 d. In a particular arrangement, the actuator711 a can include a screw 719 that slides along an axial guide 729(e.g., a keyway). The screw 719 is connected to a spring 722 which is inturn connected to the guidewire 250 d with a coupling 716. The coupling716 can transmit electrical energy to and/or from the guidewire 250 d,and accordingly can be connected to a connecting lead 715, which is inturn connected to a power source 714 via a switch 717. The power source714 can have a relatively high output impedance (e.g., 400-1000 ohms),which can allow the penetrating tip 753 to readily begin a spark erosionprocess when in contact with the septal tissue. This feature can alsoallow the tip 753 to rapidly quench when in a blood pool. Still further,the high output impedance is expected to reduce the likelihood for thetip 753 to arc when in a blood pool, thus reducing the likelihood forforming a thrombus. A sensor 726 (e.g., an impedance sensor) can detecta characteristic of the environment in which a penetrating tip 753 ofthe guidewire 250 d is positioned, as discussed above with reference toFIG. 7A.

In a particular aspect of the arrangement shown in FIG. 7B, the actuator711 a further includes a rotatable knob 712 that threadably engages thescrew 719 and is restricted from axial movement by a retainer 713.Accordingly, the operator can rotate the knob 712 in a counterclockwisedirection (indicated by arrow R1), which causes the screw 719 to axiallyadvance along the axial guide 729 while the knob 712 is held in a fixedaxial position by the retainer 713. One or more detents 721 can controlthe motion of the screw 719. For example the detents 721 can providetemporary and/or intermediate stops for the screw 719 as it is advancedby predetermined distances. A head 727 of the screw 719 can provide afinal stop by contacting the knob 712 when the maximum number ofdistance units has been reached.

In a particular embodiment, the knob 712 can be rotated manually by apractitioner. In other embodiments, a motor 720 or other powered devicecan rotate the knob 712 to automate or at least partially automate theprocess of advancing the penetrating guidewire 250 d. In suchembodiments, the motor 720, the switch 717, and the sensor 726 can beoperatively coupled together (e.g., under the direction of thecontroller 221 shown in FIG. 2) so that the guidewire 250 d can beautomatically advanced until the tip 753 penetrates through the septum106. In further embodiments the actions of the knob 712 and the screw719 can be reversed, e.g., the knob 712 can slide axially, and the screw719 can rotate.

FIG. 7C illustrates the guidewire advancer 710 a after the screw 719 hasbeen advanced by a representative distance unit D. At this point, apreload has been applied to the guidewire 250 d, for example, bycompressing the spring 722 and/or by deforming the septum 106. Theswitch 717 can remain open while the preload is applied to the guidewire250 d.

When the guidewire 250 d has been advanced far enough to contact theseptum 106, as indicated in FIG. 7C, and as detected by the sensor 726,the switch 717 can be closed, as shown in FIG. 7D. As electrical poweris provided to the tip 753, the tip 753 ablates the septal tissue andadvances by a distance unit D, relieving the compressive force (e.g. thepreload) on the tip 753 provided by the septum 106 and/or the spring722. The process shown in FIGS. 7B-7D can be repeated until the septum106 is penetrated and/or until the head 727 engages the knob 712.

FIG. 7E illustrates a guidewire advancer 710 b and associated actuator711 b configured in accordance with another embodiment of thedisclosure. In one aspect of this embodiment, the actuator 711 b caninclude a slider 723 that is coupled to the spring 722 and the guidewire250 d to advance the guidewire tip 753. The slider 723 can be operatedmanually or via the motor 720. In either arrangement, the guidewireadvancer 710 b can include one or more detents 721 to control the motionof the slider 723. For example, the detents 721 can be positioned onedistance unit apart to allow the guidewire 250 d to be advancedincrementally into and through the septum 106.

FIG. 7F illustrates a guidewire advancer 710 c configured for automatedoperation in accordance with another embodiment of the disclosure. Theguidewire advancer 710 c can include a constant force spring 722 and/ora motor 720, operatively coupled to the guidewire 250 d. Before thetissue penetration feature of the guidewire 250 d is operated, a catch728 is engaged with a wire stop 725 to prevent inadvertent movement ofthe penetrating tip 753. To begin operation, the practitioner can pressa start button 724 which both releases the wire stop 725 from the catch728, and closes an energy delivery “on” switch 717 a. At this point, thespring 722 and/or the motor 720 apply an axial force to the penetratingguidewire 250 d while the power source 714 (FIG. 7B) applies anelectrical current to the guidewire 250 d. In a particular embodiment,the tip 753 can be positioned against the septum 106 before the startbutton 724 is engaged, but in other embodiments, the tip 753 can beautomatically advanced into contact with the septum 106 using a feedbackarrangement as was discussed above with reference to FIGS. 7A-7B.

As the penetrating tip 753 presses against and ablates the septaltissue, it advances into the septum 106 while the constant force spring722 and/or the motor 720 continue to apply an axial force that moves thetip 753 forward. In a particular aspect of this embodiment, the motionof the tip 753 can be generally continuous until the tip 753 penetratesthrough the septum 106 and/or until the wire stop 725 engages an energydelivery “off” switch 717 b, e.g., after traveling a full traveldistance T as shown in FIG. 7F. In other embodiments, the motion of thetip 753 can be controlled to be stepwise or incremental, as discussedabove with reference to FIGS. 7A-7E. In still further embodiments,devices other than a constant force spring can be used to apply agenerally constant force to the tip 753. Such devices include, but arenot limited to, pneumatic devices and hydraulic devices.

FIG. 7G is a detailed cross-sectional illustration of the penetratingguidewire 250 d in accordance with a particular embodiment. Thepenetrating guidewire 250 d can include a flexible, electricallyconductive core 744 enclosed by a sheath of flexible, electricalinsulation 743. The tip 753 is in electrical communication with theconductive core 744. A collar 742 or other electrically and thermallyinsulating member can be located between the tip 753 and the flexibleelectrical insulation 743. In a particular embodiment, the penetratingguidewire 250 d can include features to enhance fluoroscopicvisualization (or other visualization) during operation. For example,the penetrating guidewire 250 d can include one or more bands or otherregions of plating (e.g., a 7μ layer of gold plating) at points in aproximal direction from the tip 753. In a particular embodiment, theplating can be a continuous coating that extends from the tip 753proximally by a distance of about two inches.

In operation, the penetrating guidewire 250 d can perform as a sparkerosion or spark discharge device. Accordingly, sparking produced at thetip 753 can produce microscopic explosive steam vesicles that open aregion in the tissue ahead of the tip 753 and allow the guidewire 250 dto penetrate. The materials for the components of the penetratingguidewire 250 d can be selected to enhance this operation. For example,the tip 753 can include a thermally refractory, radio-dense orradiopaque material, such as a platinum-iridium alloy, that resistspitting and/or other types of degradation that occur in metals withlower melting points, such as steel and Nitinol. Platinum-iridium alloysare also readily machineable and swageable, and can show up well duringfluoroscopic surveillance of the penetrating procedure. The conductivecore 744 can be formed from a more flexible material, such as Nitinol,and the insulation 743 can reduce or prevent the loss of electricalenergy along the length of the conductive core 744. The collar 742 caninclude a ceramic material that provides a thermal buffer between thetip 753 and the electrical insulation 743, which might otherwise suffermelting and/or other damage as a result of the sparking action at thetip 753.

One feature of particular embodiments described above with reference toFIGS. 7A-7G is that the penetrating guidewire is advanced incrementally.Accordingly, the likelihood for over-advancing the penetrating guidewirecan be eliminated or significantly reduced. Another advantage associatedwith particular embodiments is that the process of advancing thepenetrating guidewire can include applying a compressive preload on theguidewire. This arrangement can increase the efficiency with which theguidewire penetrates the septal tissue. Still another advantageassociated with at least some of the foregoing embodiments is that someor all aspects of the guidewire motion can be automated orsemi-automated. For example, the practitioner can manually place theguidewire 250 d at or close to the septum 106, and the automatedprocedure can be used to penetrate the septum. This arrangement can, inat least some cases, provide for increased consistency of operationand/or increased penetration accuracy.

In at least some embodiments, selected aspects of the penetratingguidewire can be modified or eliminated. For example, in someembodiments, the final “stop” feature of the foregoing embodiments canbe included, but the discrete stepwise advancement feature can beeliminated. Imaging/visualization techniques can instead be used todetermine the progress of the penetrating guidewire and can optionallysupplement the function of the final stop.

Returning now to FIG. 3E, the penetrating guidewire 250 d can beoperated in a bipolar manner, as indicated by field lines F,independently of whether or not it is controlled in accordance with themethod described above with references to FIGS. 7A-7G. In particular,electrical power can be provided to the electrode tip 253 shown in FIGS.3E, and the return electrode 280 b can operate as a return path forelectrical current provided to both the tip 253 and a treatmentelectrode, e.g., the electrode 280 shown in FIG. 3F. In otherembodiments, the penetrating guidewire 250 d can use other returnelectrodes, but in an aspect of the embodiment shown in FIG. 3E, theshared return electrode 280 b can reduce the overall complexity of thesystem.

In a particular embodiment, power can be supplied to the penetratingguidewire 250 d at from about 150 volts rms to about 250 V_(rms) (e.g.,about 200 V_(rms)) and a frequency of from about 100 KHz to about 5 MHz(e.g., about 480 KHz). The power can be applied for about 2 secondscontinuously in one embodiment, and another embodiment, the power can beapplied over a time period that ranges from about 1 second to about 5seconds. In still further embodiments, the power can be applied for timeperiods of less than 1 second. For example, from about 0.01 seconds toabout 0.1 seconds.

In any of the foregoing embodiments, the motion of the penetratingguidewire 250 d can be constrained, for example, via a stop devicecarried by the penetrating guidewire 250 d and/or the delivery catheter230 b. In particular embodiments, the motion of the penetratingguidewire 250 d can be constrained so that the tip 253 (at maximumdisplacement) is no further than five centimeters from the returnelectrode 280 b. In other embodiments, this distance can be threecentimeters or less. In any of these embodiments, the distance betweenthe tip 253 and the return electrode 280 b is relatively small, so thatthe electric field emanating from the tip 253 loops back to the returnelectrode 280 b.

One feature of the foregoing bipolar arrangement for the penetratingguidewire 250 d is that it can improve patient safety because theelectric fields are more tightly constrained to the region of interest(e.g., the septum 106). In addition, the bipolar arrangement eliminatesthe need for a patient pad, which can simplify the patient treatmentprocedure and provide for more consistency from one patient to another.Further features of bipolar electrode arrangements are described laterwith reference to FIG. 6J.

E. Electrode Devices and Associated Methods

After the penetrating guidewire is inserted through the septal tissue,an electrode device or other energy delivery device can be passed alongthe penetrating guidewire to seal the PFO tunnel. FIG. 8A is a partiallyschematic, cross-sectional illustration of an electrode device 880 aconfigured in accordance with a particular embodiment of the disclosure.The electrode device 880 a can be carried by the electrode catheter 230c described above, or by another catheter. The electrode device 880 acan include an electrically conductive material 881 formed from aplurality of flexible fibers. In a particular embodiment, the fibers arewrapped in a generally spiral and/or braided fashion with first ends 888connected to a support 887 (e.g., a distal end of the electrode catheter230 c, or a ferrule carried at the distal end), and second ends 889attached to an actuator 883. The actuator 883 can include an actuatorcap 885 connected to an actuator tube 884 that fits within the electrodecatheter 230 c and has an axial opening through which the penetratingguidewire 250 d passes. The actuator cap 885 can be formed from anelectrically insulating material, e.g., a ceramic material or polymer.In some embodiments, the actuator tube 884 can extend (as a tube)through the entire electrode catheter 230 c and outside the patient'sbody for actuation. In other embodiments, the actuator tube 884 canextend for a short distance and then connect to an actuator cable thatextends alongside the penetrating guidewire 250 d and outside thepatients' body. In still further embodiments, the actuator tube 884 canbe eliminated and replaced with a cable that attaches directly to theactuator cap 885.

The conductive material 881 forming the electrode device 880 a caninclude a Nitinol material, another shape memory material, and/oranother suitable fibrous electrically conductive material. The electrodedevice 880 a can include a suitable number of fibers or strands (e.g.,from about 16 to about 128), having a suitable diameter (e.g., fromabout 0.001 inches to about 0.010 inches). In a particular embodiment,the electrode device 880 a can include 48 strands, each having adiameter of about 0.004 inches. In a particular embodiment, theconductive material 881 has the configuration shown in FIG. 8A when inits relaxed state. When the actuator tube 884 (and/or cable) iswithdrawn proximally into the electrode catheter 230 c, the actuator cap885 draws the second ends 889 of the conductive material 881 toward thefirst ends 888, causing the conductive material 881 to splay outwardlyfrom the penetrating guidewire 250 d.

Electrical power is provided to the conductive material 881 via anelectrical energy path 886. In a particular embodiment, the actuator 883itself can be electrically conductive and can provide the electricalenergy path 886 to the conductive material 881. In other embodiments, aseparate electrical lead or other conductive member can provide theelectrical energy path.

FIGS. 8B and 8C illustrate the electrode device 880 a in its deployedconfiguration. In this configuration, the conductive material 881 can beflattened or partially flattened up against the primum 107 (as shown inFIG. 8B), and can form a petal-like configuration when seen in end view(as shown in FIG. 8C). Accordingly, the electrode device 880 a includesgaps or spaces between the strands or filaments of conductive material881. In general, the electrode device 880 a can have a diameter in therange of from about 2 mm to about 30 mm (e.g., about 12 mm) whendeployed. The particular diameter selected by the practitioner candepend on features that include the geometry of a given patient's PFO.

Referring now to FIG. 8B, the distal-facing surfaces of the conductivematerial 881 may be coated with an insulating material 882 in aparticular embodiment to prevent or restrict electrical signals frombeing directed distally into the blood in the left atrium 102. Instead,the insulating material 882 can limit the delivery of electrical energyso as to be delivered to the septum 106 rather than throughout the leftatrial region, which would otherwise provide an electrical pathway toground. In another embodiment, the insulating material 882 can beeliminated. It is expected that eliminating the insulating material 882may improve the manufacturability of the electrode device 880 a, and inmany cases may enhance the energy delivery to the primum 107 whencompared to an electrode device that includes the insulating material882. In particular, as the electrode device 880 a directs energy intothe septum 106, the impedance of the tissue in the septum 106 (e.g., inthe primum 107) directly adjacent to the electrode device 880 aincreases. Accordingly, the path of least electrical resistance may movelaterally away from this region. For example, the path of leastelectrical resistance may be through the blood located adjacent to thedistal surface of the conductive material 881 in the left atrium 102,and then back into a portion of the septum located laterally from theelectrode device 880 a, as indicated by arrows F in both FIGS. 8B and8C. It is expected that in at least some embodiments, the effect of thespreading current path will be to increase the radial dimension of theseal 118 formed between the primum 107 and the secundum 108 in spite ofthe increasing impedance of the tissue close to the conductive material881. Accordingly, this arrangement can provide a more secure and/or morecomplete tissue seal 118 between the primum 107 and the secundum 108.

The foregoing effect (e.g., directing the electrical field radiallyoutwardly) can apply to the electrode device 880 a as a whole, asdiscussed above, and also to individual fibers or strands of theelectrode device 880 a. For example, FIG. 8D is a cross-sectional viewof one of the fibers or strands of conductive material 881 shown in FIG.8C, positioned against the primum 107. As energy is applied to theconductive material 881, a tissue desiccation zone 816 typically formsin the primum 107 adjacent to the conductive material 881, dependingupon the density of the current at the strand. The increased impedancein the tissue desiccation zone 816 reduces current flow (and resultantheat production) therein; however, the ongoing current flow in theblood-to-tissue circuit continues, as shown by arrows F. Without theability of the current to flow from the distal-facing surfaces of theelectrode device filaments or strands (which are in contact withcirculating blood), the tissue may not reach temperatures adequate tocause tissue sealing in the regions between individual strands.Accordingly, making the distal surfaces uninsulated can increase theamount of heated tissue between individual strands of conductivematerial 881. This in turn can improve the uniformity of the seal formedby the electrode device 880 a even though it includes individual strandsrather than a continuous conductive plate. This effect can be important,particularly for larger electrode devices 880 a (e.g., having a diameterof 12 mm and used for sealing larger regions of tissue), for which theremay exist larger spaces between individual strands.

In particular embodiments, the entire distal surface of the electrodedevice 880 a can be uninsulated, and in other embodiments, selectedportions of the distal surface can be uninsulated, and other portionscan be insulated. For example, referring now to FIG. 8B, the lower orinferior portion of the distal surface can be insulated and the upper orsuperior portion can be uninsulated. In this manner, the heating effectproduced by the electrode device 880 a can preferentially be projectedradially outwardly in the superior direction. Because the primum 107 mayoverlap the secundum 108 to a greater extent in the superior region thanin the inferior region, this arrangement can concentrate the heatingeffect in the region(s) where a tissue seal is most likely to form(e.g., the superior region), while reducing power loss to the leftatrial blood in other regions (e.g., the inferior region). This resultcan be particularly beneficial for larger electrode devices, e.g., thosehaving a diameter in the range of from about 12 mm to about 18 mm.

In other embodiments, the distribution of insulation on the distalsurface of the electrode device may be selected in other manners. Forexample, selected inferior portions of the electrode device 880 a mayremain uninsulated to promote primum heating even where the primum 107does not overlap the secundum 108 so as to shrink the primum in suchregions. This arrangement can reduce septal tissue “floppiness” and/orimprove the tissue seal.

In particular embodiments, the practitioner may wish to monitor thetemperature in the region of the tissue seal. Accordingly, the electrodedevice 880 a can include a thermocouple 879 or other temperature sensorto provide feedback. The feedback information can be used to updateenergy delivery parameters, either with the practitioner “in the loop,”or automatically in a closed loop fashion.

As discussed above, embodiments of the electrode device 880 a include afilamentous, fibrous, stranded and/or otherwise porous and/or fluidtransmissible conductive material 881. As a result, the filaments can beexposed to and cooled by blood circulating in the left atrium 102. Anexpected advantage of this arrangement is that the filaments can be lesslikely to overheat by virtue of heat conduction from the adjacentcardiac tissue, which is in turn heated by the RF energy produced by theelectrode device 880 a. This arrangement can also be less likely tooverheat the adjacent cardiac tissue. Accordingly, the filaments can beless likely to stick to the adjacent cardiac tissue, and the tendencyfor clot formation can be reduced. Blood desiccation and/or coagulationmight otherwise adversely affect the uniformity and/or strength of theelectric field provided by the electrode device 880 a. In addition, thisarrangement can allow the electrode device 880 a to be operated athigher powers and/or for longer periods of time without coagulating,which gives the practitioner additional flexibility and safety whenperforming procedures.

FIGS. 8E and 8F illustrate electrode devices having filamentous and/orfibrous conductive material 881 arranged in accordance with otherembodiments of the disclosure. For example, FIG. 8E illustrates anelectrode device 880 b having conductive material arranged in a wovenpattern and flattened in its relaxed state. In a further aspect of thisembodiment, the flattened sheet of conductive material 881 can furtherbe folded on itself, as indicated by arrows G, so as to more easily fitwithin the electrode catheter 230 c. In an embodiment shown in FIG. 8F,an electrode device 880 c includes a filamentous electrically conductivematerial 881 that is arranged more or less randomly, rather than in aregular pattern. When deployed, the electrode device 880 c can form ashape (e.g., a “ball”) that is more three-dimensional than the generallyflat, petal-shaped configuration shown in FIG. 8C. An advantage of thisarrangement is that it may be easier to manufacture, and/or the level ofcare required to place the electrode device 880 c in the electrodecatheter 230 c may be less than is required for the electrode device 880a shown in FIGS. 8A-8D.

FIG. 8G illustrates an electrode device 880 d having electricallyconductive material 881 in the form of one or more fibers arranged in apetal configuration. The conductive material 881 can have a preformedshape once the electrode device 880 d has been deployed, and in aparticular embodiment, the preformed shape can include a generallyconcave, disk-type shape, as shown in FIG. 8G. This shape can flattenout when the electrode device 880 d is pulled against the septal tissue.In particular embodiments, depending for example on the flexibility ofthe conductive material 881, this arrangement can result in a moreuniform distribution of force on the septal tissue. The preformed shapecan be formed in any of a variety of suitable manners, including heatsetting the conductive material 881, permanently deforming theconductive material fibers during the assembly process, varying thehelix angle of the braid along the length of the braid, and/or varyingthe way the braid is constrained during the assembly process and/orduring the process of deploying the electrode device 880 d.

FIG. 8H illustrates an electrode device 880 e configured in accordancewith yet another embodiment of the disclosure. In this embodiment, theconductive material 881 can have a petal configuration positioned in aplane that is generally flat, as shown in FIG. 8C, or concave, as shownin FIG. 8G, or shaped in another manner. In any of these embodiments,the general plane in which the conductive material 881 is positioned canbe tilted relative to the axis of the electrode catheter 230 c at anon-orthogonal angle. When the electrode device 880 e is deployed at theseptum 106, as shown in FIG. 8I, the degree of tilt between the plane ofthe electrode device 880 e and the axis of the electrode catheter 230 ccan help to ensure that the upper edge of the electrode device 880 emakes good contact with the primum 107 and holds the primum 107 firmlyagainst the secundum 108 in this area. The tilt angle can be selected inconcert with the tissue penetration angle, which is about 105° in FIG.8I and was discussed further above with reference to FIG. 3D. Thisarrangement can align the electrode device 880 e with the septum 106 andprovide good coaption between the primum 107 and the secundum 108. Whenthe electrode device 880 e has an initially concave preformed shape, asdiscussed above with reference to FIG. 8G, applying a proximal force (asindicated by arrow P) on the electrode device 880 e can cause it toflatten and provide a generally uniform compression force against theseptum 106.

In other embodiments, the electrode devices can have shapes and/orconfigurations other than those that are explicitly shown and describedabove. In at least some cases, these electrode devices are shaped and/orconfigured to increase the uniformity with which coaption forces areapplied to the septum 106, and in other cases, these electrode devicesare shaped and/or configured to concentrate the coaption force in one ormore areas of the septum.

Another feature of an embodiment of the electrode device 880 e shown inFIGS. 8H and 8I is that it can include fluid delivery ports 890 that arein fluid communication with a fluid delivery lumen internal to theelectrode catheter 230 c. In operation, an electrolyte (e.g., anelectrolytic fluid) can be delivered radially outwardly through thefluid delivery ports 890 to cool the distal, exposed surfaces of theelectrode device 880 e, and/or to prevent the accumulation of proteinsor other substances at these surfaces. In another embodiment, the fluiddelivery ports 890 can be positioned at the proximal side of theconductive material 881 to infuse the region between the electrodedevice 880 e and the septum 106. In still a further embodiment, thefluid delivery ports 890 can be positioned axially between proximal anddistal portions of the conductive material 891, as described furtherwith reference to FIG. 8J. The fluid can be delivered manually orautomatically. In particular embodiments, the electrolyte can include ahypertonic saline, or another biocompatible, electrically conductivefluid. Accordingly, the fluid can both cool the septal tissue at theinterface with the electrode device 880 e (e.g., to prevent or restrictthe septal tissue from sticking to the electrode device 880 e), whilestill allowing electrical energy to pass deeper into the septal tissueto heat the tissue and seal the PFO 112. In particular embodiments, thefluid can be chilled (e.g. to a suitable temperature below normal bodytemperature) to enhance the cooling effect. Whether the fluid is chilledor not, it can pass through a thermally insulated channel in theelectrode catheter 230 c so as to reduce or eliminate the likelihoodthat it will cool the septum 106 (the secundum 108 and/or the primum107) before exiting through the delivery ports 890. Another approach isto preheat the fluid (e.g., in a range of from about 40° C. to about 90°C., or about 65° C. to about 70° C.) so that it does not chill theseptum 106. It is expected that in at least some of the foregoingembodiments, the electrolytic fluid can more readily cool and/or flushthe electrode device/tissue interface than can the blood in the leftatrium.

In another embodiment, the fluid dispensed from the fluid delivery ports890 can have characteristics other than those described above. Forexample, the fluid can include D5-W water (e.g., 5% dextrose in water),or another electrically non-conductive, or generally non-conductive,fluid that can provide cooling for the electrode device 880 e. In thisembodiment, the electrically non-conductive nature of the fluid canprevent the loss of electrical power to the adjacent blood field. Ineither embodiment, the fluid can act to prevent or reduce theaccumulation of clotting proteins at the electrode device 880 e, via oneor more mechanisms. For example, the flow of fluid can flush suchproteins from the electrode device 880 e. In addition to or in lieu offlushing the proteins, the ability of the fluid to reduce thetemperature of the electrode device 880 e can reduce or eliminateprotein accumulations. Still further, when the fluid is electricallynon-conductive, it can displace the electrically conductive blood awayfrom the electrode device 880 a, so as to create an electricallynon-conductive region around the electrode device 880 e andpreferentially direct current into the septal tissue.

In any of the foregoing embodiments, the fluid can include constituentsthat provide functions other than (e.g., in addition to) those describedabove. For example, the fluid can include an ultrasound contrast agentto allow the fluid to be visualized more readily via ultrasoundtechniques. In any of the foregoing embodiments, the fluid can beprovided at a suitable rate through suitably sized delivery ports 890.For example, the electrode device 880 e can include 8-16 ports 890having diameters of 0.005 inches, and the fluid can be provided at arate of from about 1 ml/minute to about 100 ml/minute. In particularembodiments, the fluid can be pulsed. For example, the fluid flow can beactive or active at a first rate during portions of the cardiac cyclewhen there is a low blood flow rate past the electrode device 880 e, andthe fluid flow can be inactive or active at a second rate less than thefirst rate during portions of the cardiac cycle when there is a higherblood flow rate past the electrode device 880 e. Changes in the fluidflow rate can be based at least in part on changes in left atrial and/orright atrial pressure, and/or based on EKG data. In a particularembodiment, the system can include pressure transducers positioned inboth the left and right atria, and coupled to a controller to vary thefluid flow rate in accordance with changes in the left atrial pressureand/or changes in the difference between left and right atrialpressures. Varying the flow rate can reduce the volume of fluid injectedinto the patient, while preserving a cooling effect on the electrodedevice 880 e. Any of the foregoing aspects of fluid delivery can becontrolled by the controller 221 as shown in FIG. 2, e.g., viaprogrammed, computer-based instructions

As discussed previously, it is believed that the mechanism by which theinterface between an electrode device 880 e and the adjacent septaltissue 106 heats up is not due to directly heating the electrode device880 e as current is passed through it, but is instead due to heat thatis conductively transferred back to the electrode device 880 e from theadjacent septal tissue 106, which is in turn heated by absorbing RFradiation from the electrode device 880 e. Accordingly, embodiments ofthe disclosure are directed to devices and techniques that facilitatecooling an electrode device without unduly sacrificing heat applied tothe septal tissue 106 for closing the PFO. For example, FIG. 8Jillustrates an electrode device 880 f deployed relative to the primum107 and the secundum 108 in accordance with a particular embodiment ofthe disclosure. The electrode device 880 f can include a filamentouselectrically conductive material 881 connected at one end to a support887 (e.g., the end portion of the electrode catheter 230 c) and at theother end to an actuator cap 885. The actuator cap 885 is in turn movedby an actuator tube 884 that slides within the electrode catheter 230 c.A stop tube 878 or other suitable device restricts the axial motion ofthe actuator cap 885 toward the support 887. Accordingly, when theactuator cap 885 is drawn proximately into contact with the stop tube878, the electrode device 880 f assumes an ellipsoid shape, generally asshown in FIG. 8J. The ellipsoid can have any of a variety of aspectratios. For example, in a particular embodiment, the electrode device880 f can have a generally spheroidal shape, with a diameter D1approximately equal to an overall length L1. In still furtherembodiments, D1 and L1 can have values of about 9 mm. In otherembodiments, the electrode device can have variations on this shape, asdescribed later with reference to FIGS. 8K and 8L. The electrode device880 f can optionally include fluid delivery ports 890 (FIG. 8I)positioned between the support 887 and the actuator cap 885. However, itis expected that in at least some embodiments, the cooling effectresulting from the shape and porous nature of the electrode device 880 fwill eliminate the need for fluid delivery ports.

In a particular aspect of the embodiment shown in FIG. 8J, the electrodedevice 880 f operates in a bipolar manner, for example, via the returnelectrode 280 b carried by the delivery catheter 230 a. Accordingly,electric field lines (shown as phantom lines F in FIG. 8J) generatedwhen current is applied to the electrode device 880 f tend to form apattern that is directed back toward the return electrode 280 b. Oneexpected result of this arrangement is that more of the electricalcurrent generated by the electrode device 880 f will be directed intothe primum 107 and the secundum 108, rather than distally into theadjacent blood field. Another result is that the patient need not have apatient pad or plate in contact with the patient's skin to provide areturn electrical path. This can simplify the system and reduce thenumber of components the practitioner must track. In addition, in atleast some embodiments, this bipolar arrangement can increase thepredictability and repeatability of the tissue sealing procedure. Forexample, it is expected that the patient-to-patient impedance variationsbetween the two bipolar electrodes will be less than the variationbetween a monopolar electrode and a remote patient pad. In particular,the electrode 880 f can have a relatively low impedance. If theimpedance at the skin/pad interface varies significantly, this can havea dramatic effect on the impedance of the overall circuit, and thereforeon the efficacy and/or efficiency of the tissue sealing process.

One feature of the ellipsoid/spheroid shape of the electrode device 880f is that it has fewer corners or edges than flat electrode devices, forexample the electrode device 880 e described above with reference toFIGS. 8H and 8I. As a result, it is expected that the likelihood forcurrent density concentrations at such edges is significantly reduced oreliminated, producing a more uniform electrical field within the septaltissue 106. Another feature of this arrangement is that a relativelysmall portion of the electrode device 880 f is actually in contact withthe primum 107. As a result, the electrode device 880 f is expected toreceive less heat from the septal tissue 106 than is an electrode thatis placed flat up against the primum 107. Nevertheless, the ellipsoidal(and in a particular embodiment, spheroidal) shape of the electrodedevice 880 f can not only contact the primum 107 and provide a coaptingforce, but it can also conform the primum 107 to have a concave shape,which can in turn stretch the primum 107 and extend the radius of thecoapting force between the primum 107 and the secundum 108 beyond theregion of the primum 107 that is in direct contact with the electrodedevice 880 f. In addition, this arrangement, in combination with theoverall porous nature of the electrode device 880 f provided by thefilamentous conductive material 881 allows for greater cooling by theadjacent blood. This in turn reduces the likelihood for forming clots atthe electrode device 880 f and/or causing the electrode device 880 f tostick to the primum 107. The bipolar electric field (which tends todirect more energy to the septum 106 and less into the left atrialblood) is also expected to reduce the likelihood for clotting.Optionally, the electrode device 880 f can include heparin or anotherantithrombotic coating to reduce or prevent clot formation. At the sametime, the shape of the electrode device 880 f is expected to provide acoaption force sufficient to clamp the primum 107 and the secundum 108against each other between the electrode device 880 f and the deliverycatheter 230 a.

Still another feature of at least some embodiments of the foregoingarrangement is that the shape and radius of the electrode device 880 fcan be controlled by varying the movement of the actuator tube 878. Forexample, the practitioner can deploy the electrode device 880 f bydifferent amounts to produce corresponding different shapes, includingthose described below with reference to FIGS. 8K and 8L. The particularshape selected by the practitioner can depend on size and/or geometry ofa particular patient's PFO.

When power is applied to the electrode device 880 f (and/or otherelectrode devices described herein), it can be applied in a number ofmanners. For example, in one embodiment, the power can be applied to theelectrode device 880 f as a generally continuous high-frequency streamof pulses. In other embodiments, the power can be modulated to achieveparticular results. For example, in a particular embodiment, the powercan be provided at different amplitudes during different phases of thetissue sealing process. In particular, the power can be provided duringa first phase at a first power level and during a second phase at asecond power level higher than the first. During the first phase, thepower applied to the septal tissue 106 can produce one or both of thefollowing effects. First, it can pre-shrink the septal tissue 106 (e.g.,the primum 107 and/or the secundum 108) without sealing the tissuetogether. More particularly, the power can be applied at an amplitudehigh enough to heat the septal tissue 106 sufficiently to cause it toshrink, but not so high as to cause it to seal. For example, the tissuecan reach a temperature of less than 100° C. during the first phase.Second, applying heat to the septal tissue 106 in this manner canpre-desiccate the tissue, e.g., purge or at least partially purge thetissue of water before the primum 107 is sealed to the secundum 108.During the second phase, the pre-shrunk and/or pre-desiccated tissue issealed by applying power at a higher amplitude and heating the tissue toa higher temperature (e.g., about 100° C.).

In particular embodiments, the power can be selected in a manner thatdepends upon patient-specific characteristics and/or specificcharacteristics of the electrode device 880 f and/or other features ofthe overall system. For example, power can be applied in the range offrom about 10 watts to about 60 watts for a period of about 2 seconds toabout 120 seconds during the initial phase, and can be applied at ahigher power (e.g., 12 watts to about 100 watts for a period of about 2seconds to about 180 seconds) to seal the septal tissue during thesecond phase. Particular values selected within the foregoing ranges candepend upon factors that include whether the electrical power isprovided in a monopolar manner or a bipolar manner, the size and shapeof the electrode device, and/or the shape or characteristics of aparticular patient's secundum 108 and/or primum 107.

One expected advantage of the foregoing arrangement is thatpre-shrinking the septal tissue 106 can reduce the likelihood that thetissue will shrink during the tissue sealing process. Accordingly, thesealed tissue is expected to have fewer shear stresses and is thereforeexpected to remain intact for a longer period of time and/or (in thecase of an initially incomplete seal) it is expected to more quicklyform a complete seal as a result of the body's natural healingprocesses. By pre-desiccating the septal tissue, embodiments of theforegoing process can reduce or eliminate the presence of water in theseptal tissue when higher power is applied to the septal tissue forsealing. This in turn can reduce the likelihood that such residual waterwill vaporize as the tissue is sealed under higher amplitude power, thusreducing the likelihood for disrupting the tissue seal as the vaporizedwater attempts to escape from the sealed region.

In another embodiment, the power applied to the electrode can beprovided at a duty cycle of less than 100% (e.g., with the power offduring certain intervals) so as to increase the efficacy of the process.For example, it has been observed that the surface of the primum 107exposed in the left atrium can cool much more quickly than the tissuelocated at the interface between the primum 107 and the secundum 108, atleast in part due to the enhanced cooling effect provided by blood inthe left atrium as it passes directly adjacent to the exposed leftatrial surface of the primum 107. By interrupting the power provided bythe electrode device 880 f to the septal tissue 106, the exposed surfaceof the primum 107 can cool relatively rapidly, while the temperature ofthe tissue at the interface between the primum 107 and the secundum 108remains relatively high. For example, in at least some cases, there canexist a 30°-45° temperature difference between the exposed left atrialsurface of the primum 107 and the interface between the primum 107 andthe secundum 108. The ability to achieve this temperature differentialcan be enhanced by using a duty cycle of less than 100% Representativeduty cycles include a 75% duty cycle (with power on for 15 seconds andoff for 5 seconds), a 67% duty cycle (with power on for 14 seconds andoff for 7 seconds), and an 84% duty cycle (with power on for 5 secondsand off for 1 second). In other embodiments, the duty cycle can haveother characteristics with ranges of from about 50% to about 90%,durations ranging from about 1 second to about 10 minutes, and the totalnumber of cycles ranging from 1 to about 1,000.

In other embodiments, electrodes having shapes similar at least in partto those described above can be operated in a generally similar mannerto that described above with reference to FIG. 8J. For example, as shownin FIG. 8K, an electrode device 880 g can have an aspect ratio D1/L1 ofup to approximately 1.5 or more, to form an oblate spheroidal shape. Ina particular aspect of this embodiment, D1 can have a value of about10.6 mm. As shown in FIG. 8L, another electrode device 880 h can have anaspect ratio D1/L1 that is less than 1.0 to form a generally prolatespheroid. In a particular aspect of this embodiment, D1 can have a valueof less than 9 mm. In still further embodiments, the electrode devicecan have shapes other than those specifically described above and shownin the Figures.

FIG. 9A is a partially schematic, cross-sectional side view of anelectrode device 980 configured in accordance with another embodiment ofthe disclosure. The electrode device 980 can include a conductive sheet981 carried by a support structure 990. In a particular embodiment, theconductive sheet 981 can include a conductive fabric, for example, afabric woven from conductive strands or fibers. The conductive fibers orstrands can be fully conductive (e.g., metal strands) or partiallyconductive (e.g., polyester or other non-conductive strands coated ordeposited with a conductive material). In another embodiment, theconductive sheet 981 can include a non-conductive substrate coated witha conductive material, for example, a flexible polymer sheet coated witha deposited conductive material, such as gold and/or silver. In aparticular aspect of this embodiment, the substrate material can beflexible but generally not stretchable (e.g., Mylar®), so as to reducethe likelihood for the conductive material to flake off.

The support structure 990 can include struts 991 (e.g., Nitinol struts)connected between the conductive sheet 981 and an actuator 983. In aparticular embodiment, the struts 991 are biased or pre-formed to aposition that is at least approximately orthogonal relative to thepenetrating guidewire 250 d. When the electrode device 980 is stowed,the struts 991 are folded within the electrode catheter 230 c and theconductive sheet 981 is furled. When the electrode device 980 isdeployed, the struts 991 can move outwardly, as shown in FIG. 9B tounfurl the conductive sheet 981. The electrode device 980 can bedeployed to form the generally flat shape shown in FIG. 9B, or it caninclude a stop (generally similar to that described above with referenceto FIG. 8J) so as to form a pyramidal shape like that shown in FIG. 9Awhen fully deployed. Such an arrangement can produce at least some ofthe beneficial effects described above with reference to FIG. 8J.

FIGS. 10A and 10B illustrate an electrode device 1080 configured inaccordance with another embodiment of the disclosure to deploy in amanner somewhat similar to that described above with reference to FIGS.9A-9B. In a particular aspect of this embodiment, the electrode device1080 includes a flexible conductive material 1081 electrically connectedto an electrical energy path 1086 (e.g., a leadwire) and attached to asupport structure 1090. The support structure 1090 can include flexible,resilient struts 1091 having first ends attached to an actuator 1083 atan electrode attachment or anchor 1093. The second ends of the struts1091 can be connected to a slider 1092 (e.g., another anchor) thatslides axially along the actuator 1083. Each of the struts 1091 caninclude a spring loop 1099 that tends to force the struts 1091 into atriangular shape. When stowed, the struts 1091 are forced by theinterior walls of the electrode catheter 230 c to be approximatelyparallel to the penetrating guidewire 250 d. When deployed, as shown inFIG. 10B, the actuator 1083 moves the electrode device 1080 out of thecatheter 230 c. Once the electrode device 1080 emerges from the catheterelectrode 230 c, the struts 1091 can assume a generally triangularshape. The electrode attachment 1093 remains fixed, while the slider1092 slides in a proximal direction (indicated by arrow H) toaccommodate the radially expanded shape of the struts 1091.

FIGS. 11A-11C illustrate an electrode device 1180 that includes aconductive material 1181 deployed, at least in part, by an inflatablemember 1170 in accordance with another embodiment. The conductivematerial 1181 can be secured to an actuator 1183 at an electrodeattachment or anchor 1193. Flexible support lines 1191 extend in adistal direction from the conductive material 1181 to a collar 1194(e.g., another anchor) that is fixed relative to the actuator 1183. Awire or other conductive element provides an electrical energy path 1186to the conductive material 1181. The inflatable member 1170 can beinflated with saline, contrast, or another suitable fluid. In aparticular embodiment, the inflation fluid can be circulated through theinflatable member 1170 via supply and return conduits, and canaccordingly provide functions in addition to inflating the inflatablemember 1170. Such functions can include cooling the electrode device1180.

When the actuator 1183 is moved in a distal direction (indicated byarrow J), it moves the electrode device 1180 out of the catheter 230 c,as shown in FIG. 11B. As shown in FIG. 11C, the inflatable member 1170can then be inflated to unfurl the conductive material 1181. Theinflatable member 1170 can bear outwardly on the electrode support lines1191, placing the electrode support lines 1191 under tension, whichsecures the conductive material 1181 in the deployed or unfurledconfiguration. In this embodiment, and in other embodiments that includean inflatable member, (e.g., the inflatable member 270 shown in FIG. 3G)the practitioner may in some cases select the degree to which theinflatable member is inflated based on the particular patient's PFOphysiology. For example, the inflatable member 1170 can be partiallyinflated to allow the conductive material 1181 to assume a convex shapewhen drawn against the septum, or it can be more fully inflated so as toassume a flatter shape.

One aspect of an embodiment shown in FIGS. 11A-11C is that theinflatable member 1170 and the electrode device 1180 need not beintimately connected to each other, as is the case with an electrodedevice that includes a conductive coating applied to, and in continuousdirect contact with, the exterior surface of the inflatable member.Instead, the inflatable member 1170 and the electrode device 1180 can bemovable relative to each other. For example, the inflatable member 1170shown in FIGS. 11A-11C can erect or deploy the electrode device 1180 byacting on the electrode support lines 1191. When fully inflated, theinflatable member 1170 can be in surface-to-surface contact with theelectrode device 1180 to provide shape and support to the electrodedevice 1180, but the inflatable member 1170 and the electrode device1180 can collapse separately. An expected advantage of this feature isthat the material forming the electrode device 1180 need not be bondeddirectly to the inflatable member 1170, and as a result, is less likelyto deteriorate, e.g., due to flaking off the inflatable member 1170. Anadditional expected advantage is that this arrangement can allow greaterflexibility for the manufacturer when choosing materials andconfigurations for both the electrode device 1180 and the inflatablemember 1170.

FIG. 12 illustrates an electrode device 1280 having at least somefeatures generally similar to those of the electrode device 1180described above, except that the conductive material 1181 slidesrelative to the actuator 1183 at a sliding interface 1292, while thecollar 1194 is fixed. When the electrode device 1280 is moved out of thecatheter 230 c, and the inflatable member 1170 is inflated, theconductive material 1181 can slide distally toward the inflatable member1170 along the actuator 1183, as indicated by arrow H. It is expectedthat this arrangement can increase the likelihood for the conductivematerial to have a generally flat surface facing toward the primum 107(FIG. 8A) when deployed. In other embodiments, the inflatable member1170 can have other shapes (e.g., rounded, spheroid, or ellipsoidshapes) to produce correspondingly shaped electrode device surfaces. Instill further embodiments, the shape of the inflatable member 1170 canbe changed (e.g., by varying the inflation pressure) to conform to anindividual patient's septal geometry.

FIG. 13 illustrates an electrode device 1380 that is somewhat similar tothe electrode device 1280 described above, but instead of the conductivematerial 1181 sliding at a sliding interface 1292, the electrode supportlines 1191 are attached to a slider 1392 so as to slide relative to theactuator 1183 when the electrode device 1380 is deployed. In at leastsome cases, the sliding action provided by the slider 1392 can allow theconductive material 1181 to take on a flatter shape when deployed, asdiscussed above with reference to FIG. 12.

FIG. 14 illustrates an electrode device 1480 that is similar in somerespects to the electrode device 980 described above with reference toFIGS. 9A-9B, but that deploys and retracts in a sense generally oppositeto that described above with reference to FIGS. 9A-9B. For example, theelectrode device 1480 can include a conductive material 1481 attached toan actuator 1483 with a support structure 1490 that includes multipleflexible struts 1491. The conductive material 1481 can also be attachedto a retractor 1495. The struts 1491 can be biased to the position shownin FIG. 14, and can lie generally parallel to the guidewire 250 d whenstowed. When the electrode device 1480 is deployed from the electrodecatheter 230 c as indicated by arrow K, the struts 1491 can springoutwardly to the position shown in FIG. 14, unfurling the conductivematerial 1481. To retract the electrode device 1480, the practitionercan draw the retractor 1495 in a proximal direction P, pulling theconductive material 1481 and the struts 1491 inwardly toward theactuator 1483 and the guidewire 250 d. Once the struts 1491 are alignedwith the guidewire 250 d, the practitioner can move the retractor 1495and the actuator 1483 as a unit in the proximal direction P to draw theelectrode device 1480 into the electrode catheter 230 c.

FIG. 15A is a partially schematic, cross-sectional side view of anelectrode device 1580 configured in accordance with another embodimentof the disclosure. FIG. 15B is a partially schematic, end view of aportion of the electrode device 1580 shown in FIG. 15A. With referenceto FIG. 15A, the electrode device 1580 can include a tubular portion1596 connected to an electrode actuator 1583, and fingers 1597 thatextend from the tubular portion 1596. In a particular embodiment, thefingers 1597 can be manufactured by slitting the tubular portion 1596,and bending the fingers 1597 in an outward direction. When the electrodedevice 1580 is stowed, the walls of the electrode catheter 230 c canforce the fingers 1597 into axial alignment with the guidewire 250 d.When the electrode device 1580 is deployed, the fingers 1597 can expandradially outwardly as shown in FIG. 15A. An inflatable member 1570(e.g., a balloon) can be positioned adjacent to the electrode device1580 to provide support for the electrode device 1580 when the electrodedevice 1580 is clamped against the adjacent septal tissue. Theinflatable member 1570 can include an inflatable member actuator 1571that provides an inflation medium (e.g., saline) to the inflatablemember 1570, and that can be used to draw the inflatable member 1570proximally against the electrode device 1580. FIG. 15B illustrates anend view of the electrode device 1580 (without the inflatable member1570), showing the fingers 1597 in the deployed position.

FIGS. 16A-20B illustrate electrode devices having tubular portions andoutwardly splayed fingers or flanges in accordance with furtherembodiments of the disclosure. For example, FIGS. 16A and 16B illustrateside and end views, respectively, of an electrode device 1680 thatincludes an outer tubular portion 1696 a having outer fingers 1697 a anda nested inner tubular portion 1696 b positioned annularly inwardly fromthe outer tubular portion 1696 a and having inner fingers 1697 b. Thecombination of the outer and inner fingers 1697 a, 1697 b can increasethe conductive surface area presented to the septal tissue when theelectrode device 1680 is deployed.

FIGS. 17A and 17B illustrate side and end views, respectively, of anelectrode device 1780 formed by winding a conductive filament 1781 intoa tubular portion 1796 and a flange 1798. In this embodiment, theelectrode device 1780 can include a single filament of conductivematerial that is wound in a helical fashion to form both the tubularportion 1796 and the flange 1798. In other embodiments, filamentousconductive material can form electrode devices having generally the sameshape as is shown in FIGS. 17A and 17B, with different constructiontechniques. For example, FIGS. 18A and 18B illustrate an electrodedevice 1880 having a tubular portion 1896 and a flange 1898 formed byweaving conductive filaments 1781. In FIGS. 19A-19B, the illustratedelectrode device 1980 includes a tubular portion 1996 and a flange 1998formed by a knitting process. In FIGS. 20A-20B, the illustratedelectrode device 2080 includes a tubular portion 2096 and flange 2098formed from a flat pattern rather than spiral weave pattern.

F. Systems and Techniques for Clampinq Tissue

In particular embodiments, the tissue sealed or fused by the electrodeor other energy transmission device can be clamped as it is heated, soas to promote tissue sealing. FIG. 21 is a partially schematicillustration of an embodiment of the system 220 that includes acompression device 2160 for clamping the primum 107 and the secundum 108between an electrode device 2180 and the delivery catheter 230 a. Thedelivery catheter 230 a can have a configuration generally similar tothat described above with reference to FIG. 3H and can accordinglyinclude a backstop surface 238 positioned proximate to the secundum 108.The positioning catheter 230 b can then be positioned to deploy theelectrode catheter 230 c along the penetrating guidewire 250 d throughthe septum 106 (e.g., the secundum 108 and the primum 107, or just theprimum 107). An electrode device 2180, shown schematically in FIG. 21,can then be deployed in the right atrium 102.

The electrode device 2180 can have a generally flat, not-cutting surfacefacing toward the primum 107, suitable for tissue sealing and/or fusing.The compression device 2160 can be operatively coupled between theelectrode device 2180 and one of the catheters 230 a-230 c (e.g., thedelivery catheter 230 a). For example, the compression device 2160 caninclude an actuator 2183 (e.g., a cable) that is connected to theelectrode 2180 and that extends through the electrode catheter 230 c,the positioning catheter 230 b, and the delivery catheter 230 a and isconnected to a compression member 2161. In a particular embodiment, thecompression member 2161 includes a spring connected to a cam 2162 thatis operated via a cam handle 2163 and is accordingly located outside thepatient for manipulation by the practitioner. With the electrode device2180 deployed, the practitioner can rotate the cam handle 2163, asindicated by arrow R, to stretch the compression member 2161, therebyapplying an axial tension to the actuator 2183 and compressing theseptum 106 between the electrode device 2180 and the backstop surface238.

The amount of force and/or pressure provided by the compression device2160 can be selected based on a variety of factors, including theparticular patient physiology and the particular electrode deviceconfiguration. For example, in a particular embodiment, the pressureapplied to the septal tissue by the compression device 2160 can be fromabout 0.1 psig to about 15 psig. In a particular embodiment, thepressure can be from about 0.5 psig to about 5 psig, and in a furtherparticular embodiment, about 8 psig. When the electrode device 2180 hasa petal-shaped configuration (as shown in FIG. 8C) with an overalldiameter of about 12 mm, the load applied to the electrode device 2180can be in the range of from about 0.5 pounds to about 2.0 pounds, and ina particular embodiment, about 1.4 pounds.

One advantage of embodiments including the foregoing feature is thatthey can improve the efficiency with which a seal is created between thesecundum 108 and the primum 107. For example, clamping the tissue to besealed can improve the strength of the seal by (a) reducing theconvective cooling provided by blood in the tissue, (b) raising theboiling point of tissue water, (c) raising the temperature for evolutionof entrained tissue gases, (d) improving thermal conductivity, and/or(e) increasing tissue adhesion at the tissue interface. In addition, theprimum 107 and/or the secundum 108 may shrink during the heating andfusing process, and the compression device 2160 can maintain acompressive force on these two tissues throughout the sealing process,even if the tissues tend to shrink. For example, the compression device2160 can apply a generally constant force over a distance several timesthe thickness of the septum 106, e.g., over a distance of about 20 mm.Accordingly, the compression device 2160 can maintain a generallyconstant force on the tissue during at least some phases of operation,and can be adjustable to vary the compressive force applied to thetissue (e.g., between a first clamping force and a second lesser or zeroclamping force) during other phases of operation. By applying a constantforce over a particular range, embodiments of the compression device canalso be suitable for sealing tissues (e.g., septal tissues) having avariety of thicknesses. Accordingly, such devices can be used with awide variety of patient cardiac topologies.

In other embodiments, other devices and/or techniques can be used toapply tension to the actuator 2183 and compression to the secundum 108and the primum 107. For example, the compression device 2160 can beactivated until the two tissues are “snugged” against each other, andthen further tightened or activated by extending the spring apredetermined distance, corresponding to a predetermined load. In otherembodiments, the actuator 2183 itself can be resilient, compliant,and/or stretchable, and can provide the compressive force on the septum106. Accordingly, the compression device 2160 need not include acompression member 2161 in addition to the actuator 2183. In this andother embodiments, at least part of the compression device can belocated inside the patient, e.g., at the working portion or otherportions of the catheter.

FIG. 22 illustrates a compression device 2260 that includes a threadedshaft 2265 connected to the compression member 2161 (e.g., a spring)with a swivel joint 2264. The threaded shaft 2265 is connected to ahandle 2263 and is received in a threaded opening 2266 of the deliverycatheter 230 a. When the practitioner rotates the handle 2263counterclockwise, the threaded shaft 2265 moves outwardly from thedelivery catheter 230 a, applying a tension to the compression member2161 and the actuator 2183 so as to clamp the primum 107 (FIG. 21) andthe secundum 108 (FIG. 21). The compressive force can be released byrotating the handle 2263 in the opposite direction. As discussed abovewith reference to FIG. 21, the actuator 2183 can be made stretchable andthe spring can be eliminated in another embodiment. The compressiondevice 2260 can include detents and/or circumferential markings toindicate to the practitioner how much force (or an equivalent, e.g.,stretch distance) is being applied to the actuator 2183.

FIG. 23 illustrates a compression device 2360 that in turn includes aslider 2367 having a pawl 2369 that engages with one or more teeth ornotches 2368 carried by the delivery catheter 230 a. The compressiondevice 2360 can further include a piston (e.g. non-sealing piston) 2362and a compression member 2361 (e.g., a spring between the piston 2362and the slider 2367). The piston 2362 can be attached to the actuator2183, which passes through a passageway in the slider 2367. Thepractitioner can move the slider 2367 in a proximal direction indicatedby arrow P to compress the compression member 2361, which applies atension to the actuator 2183, which in turn compresses the primum 107(FIG. 21) and secundum 108 (FIG. 21). This arrangement can provide astop (or multiple stops) along the path of the slider 2367 to preventthe practitioner from inadvertently clamping the tissue too tightly,and/or to provide a final stop that prevents the practitioner fromover-compressing the septal tissue.

Any of the foregoing devices described above with reference to FIGS.21-23 can be configured as “two position” devices (e.g., having a“compressed” position and an “uncompressed” position), or as a variableposition device (e.g., having intermediate positions). The actuationforces can be applied by devices other than springs. For example, theactuation forces can be provided by pneumatic or hydraulic actuators,which are suitable for applying a constant force over a selectedactuation distance.

From the foregoing, it will be appreciated that specific embodiments ofthe disclosure have been described herein for purposes of illustration,but that various modifications may be made from these embodiments. Forexample, as discussed above, the energy transmitter can include devicesother than RF electrodes, e.g., microwave devices. When the energytransmitter includes electrodes, the electrodes can be arranged in amonopolar manner or a bipolar manner as described above, or theelectrodes can be arranged in another multipolar manner (e.g., aquadrapolar manner). For example, the spheroidal electrode shown in FIG.8J can include multiple neighboring portions (in a circumferentialdirection) that are electrically insulated from each other. Certainaspects of the foregoing embodiments may be applied to tissues otherthan septal tissue (e.g., other target tissues), and/or in a manner totreat patient conditions other than PFOs. For example, in some cases,aspects of the foregoing embodiments can be used for procedures otherthan sealing or closing a PFO, and/or procedures other than tissuefusing. Representative procedures include percutaneous aortic or mitralvalve treatments and/or implants, left atrial appendage closures, aorticaneurysm repair, artery or vein treatment, and electrophysiologyablation therapies for correcting EKG rhythm disorders.

Certain aspects of the disclosure described in the context of particularembodiments may be combined or eliminated in other embodiments. Forexample, a catheter system in accordance with particular embodiments mayinclude only some of the foregoing devices and features, and othersystems may include devices and features in addition to those disclosedabove. In a further particular example, features of the guidewireadvancers discussed above with reference to FIGS. 7A-7F may be includedin the electrode clamping devices described with reference to FIGS.21-23, and/or vice versa. Electrode devices other than those shown inFIGS. 8H-8I can include the fluid delivery ports shown in FIGS. 8H-8I.Further, while advantages associated with certain embodiments have beendescribed in the context of those embodiments, other embodiments mayalso exhibit such advantages, and not all embodiments need necessarilyexhibit such advantages. Accordingly, the disclosure can include otherembodiments not shown or described above.

1. A patient treatment device, comprising: an elongated intravenousguidewire that includes: a first flexible branch; a second flexiblebranch fixedly secured relative to the first flexible branch at a firstlocation and releasably secured relative to the first flexible branch ata second location in a first configuration, at least one of the firstand second flexible branches being movable relative to the other betweena first position in which the first and second branches form a closedshape, and a second position in which the first and second branches forman open shape with one or both branches moved relative to the other ofthe one or both branches to produce a second configuration differentthan the first configuration at the second location; and a connectorreleasably securing the first and second branches at the secondlocation, the connector being movable relative to the first and secondbranches between a secured position with the first and second branchesin the first position and a released position with the first and secondbranches in the second position, the connector being movable with thefirst and second branches for changing a distance between the brancheswhen the first and second branches form a closed shape.
 2. The device ofclaim 1 wherein the connector is slideable between the secured positionand the released position.
 3. The device of claim 1, further comprising:a deployment tube connected to the first and second branches at thefirst location; and a connector tube slideably received in thedeployment tube and attached to the connector.
 4. The device of claim 1wherein the connector has an opening, the guidewire includes a firstguidewire, and the device further comprises a second guidewire slideablyreceived in the opening of the connector.
 5. The device of claim 1,further comprising a catheter having a lumen with the first and secondflexible branches being slideably received in the lumen, the first andsecond branches having a collapsed configuration when in the lumen and adeployed configuration when outside the lumen, the first and secondbranches being resiliently and flexibly biased to the deployedconfiguration.
 6. The device of claim 1 wherein: the guidewire includesa first guidewire; the first branch has an outwardly facing surface andan inwardly facing first flat surface at the second location; the secondbranch has an outwardly facing surface and an inwardly facing secondflat surface at the second location; the connector has an aperture and asleeve, the sleeve being positioned snugly around the outwardly facingsurfaces of the first and second branches when the connector is in thesecured position, the sleeve being spaced apart from the outwardlyfacing surfaces of the first and second branches when the connector isin the released position and wherein the device further comprises: adeployment tube having a first tab engaged with the first flat surfacewhen the connector is in the secured position, the deployment tubefurther having a second tab engaged with the second flat surface whenthe connector is in the secured position, wherein axial motion of thedeployment tube moves the second location relative to the firstlocation; a connector tube carrying the connector and positioned withinthe deployment tube, the connector tube being sideable relative to thedeployment tube to move the connector axially relative to the first andsecond branches between the secured position and the released position;and a second guidewire slideably positioned within the connector tubeand extending through the aperture of the connector.
 7. A patienttreatment device, comprising: an elongated first intravenous guidewirethat includes: a first branch; a second branch fixedly secured relativeto the first branch at a first location and releasably secured relativeto the first branch at a second location in a first configuration, thesecond location being spaced apart from the first location; and aconnector releasably securing the first and second branches at thesecond location, the connector being movable relative to the first andsecond branches between a secured position with the first and secondbranches forming a closed shape and a released position with the firstand second branches forming an open shape with one or both branchesmoved relative to the other of the one or both branches to produce asecond configuration different than the first configuration at thesecond location, the connector being movable with the first and secondbranches for changing a distance between the branches when the branchesform a closed shape; and an elongated second intravenous guidewire overwhich the first intravenous guidewire is threaded.
 8. The device ofclaim 7 wherein the connector has connector surfaces in snugsurface-to-surface contact with corresponding surfaces of the first andsecond branches when in the second position, the connector having anopening in which the second intravenous guidewire is slideably received.9. The device of claim 8 wherein: the first branch has an outwardlyfacing surface and an inwardly facing first flat surface at the secondlocation; the second branch has an outwardly facing surface and aninwardly facing second flat surface at the second location; theconnector has a sleeve positioned snugly around the outwardly facingsurfaces of the first and second branches when the connector is in thesecured position, the sleeve being spaced apart from the outwardlyfacing surfaces of the first and second branches when the connector isin the released position and wherein the device further comprises: adeployment tube having a first tab engaged with the first flat surfacewhen the connector is in the secured position, the deployment tubefurther having a second tab engaged with the second flat surface whenthe connector is in the secured position, wherein axial motion of thedeployment tube moves the second location relative to the firstlocation; and a connector tube carrying the connector and positionedwithin the deployment tube, the connector tube being slideable relativeto the deployment tube to move the connector axially relative to thefirst and second branches between the secured position and the releasedposition.
 10. A method for treating a patient, comprising: deploying anintravenous guidewire between two layers of tissue, the guidewire havinga first branch and a second branch fixedly secured relative to the firstbranch at a first location and releasably secured relative to the firstbranch at a second location spaced apart from the first location to forma closed shape in a first configuration, the guidewire also having aconnector movable with the first and second branches for changing adistance between the branches when the first and second branches formthe closed shape; performing a procedure on at least one of the twolayers of tissue in a region between the first and second branches,including at least partially fusing the two layers of tissue to eachother by applying energy to the two layers with an energy deliverydevice; separating the first and second branches from each other at thesecond location to form an open shape with one or both branches movedrelative to the other of the one or both branches to produce a secondconfiguration different than the first configuration; moving the firstand second branches relative to the layers of tissue while the first andsecond branches are separated from each other at the second location;and removing the energy delivery device from the patient's body.
 11. Themethod of claim 10 wherein deploying an intravenous guidewire includestightening at least one of the two layers of tissue with the first andsecond branches.
 12. The method of claim 10 wherein deploying anintravenous guidewire includes deploying the guidewire in a PFO tunnel.13. The method of claim 10 wherein performing a procedure includespenetrating the at least one layer of tissue in a region between thefirst and second branches.
 14. The method of claim 13 whereinpenetrating the at least one layer of tissue includes penetrating the atleast one layer of tissue at a location generally midway between thefirst and second branches, in a direction generally normal to a plane inwhich the first and second branches are located.
 15. The method of claim13, further comprising passing the energy delivery device through the atleast one layer of tissue before separating the first and secondbranches at the second location.
 16. The method of claim 15, furthercomprising: constraining the first and second branches to be in agenerally flat plane by releasably engaging inwardly facing flatsurfaces of the first and second branches with corresponding tabscarried by a deployment tube, and releasably engaging outwardly facingsurfaces of the first and second branches with a sleeve portion of theconnector carried by a connector tube that is slideably positioned inthe deployment tube, with the first and second branches interlocked withthe corresponding tabs to generally prevent relative axial movementbetween the deployment tube and the first and second branches; movingthe intravenous guidewire out of a distal portion of a catheter whilethe distal portion is positioned in the patient's heart; and moving thedeployment tube in a proximal direction to move the second locationtoward the first location and form a generally flat, planar enclosedregion between the first and second branches; and wherein separating thefirst and second branches from each other at the second locationincludes sliding the connector tube relative to the deployment tube in adistal direction to disengage the sleeve portion of the connector withthe outwardly facing surfaces of the first and second branches.
 17. Themethod of claim 13 wherein performing a procedure includes penetratingboth the first and second layers of tissue in a region between the firstand second branches.
 18. The method of claim 10 wherein moving the firstand second branches includes removing the guidewire from between the twolayers of tissue while the first and second branches are separated atthe second location.
 19. A method for treating a patient, comprising:deploying a guidewire assembly into a patient's PFO tunnel, theguidewire assembly including: a first guidewire having a first branchand a second branch fixedly secured relative to the first branch at afirst location; a connector releasably securing the first and secondbranches relative to each other at a second location spaced apart fromthe first location to form a closed shape in a first configuration, theconnector being movable with the first and second branches for changinga distance between the branches when the first and second branches formthe closed shape; and a second guidewire along which the first guidewireis threaded; penetrating at least one of the patient's primum andsecundum with a third guidewire in a region between the first and secondbranches; passing an electrode along the third guidewire into thepatient's left atrium; separating the first and second branches fromeach other at the second location by moving the connector to form anopen shape with one or both branches moved relative to the other of theone or both branches to produce a second configuration different thanthe first configuration; removing the guidewire assembly from betweenthe primum and the secundum by passing the first branch along a firstside of the third guidewire and passing the second branch along a secondside of the third guidewire opposite the first side while the first andsecond branches are separated from each other at the second location andwhile the electrode is in the left atrium; at least partially sealingthe primum and secundum to each other with the electrode; and removingthe electrode from the patients body.
 20. The method of claim 19 whereinpenetrating at least one of the patients primum and secundum includespenetrating both the primum and the secundum at a location generallymidway between the first and second branches, in a direction generallynormal to a plane in which the first and second branches are located.21. The method of claim 19, further comprising constraining the firstand second branches to be in a generally flat plane by releasablyengaging inwardly facing flat surfaces of the first and second brancheswith corresponding tabs carried by a deployment tube, and releasablyengaging outwardly facing surfaces of the first and second branches witha sleeve portion of the connector, with the first and second branchesinterlocked with the corresponding tabs to generally prevent relativeaxial movement between the deployment tube and the first and secondbranches.